Thermo roll

ABSTRACT

A heatable and/or coolable roll, i.e. a thermo roll, of a fibrous web machine for the treatment of a fibrous web, is, for example, for pressing and/or calendering the fibrous web in contact, i.e. in a nip, between the thermo roll and a backing member which is in contact with the thermo roll or for drying or cooling the fibrous web on the shell surface of the thermo roll. A semi-finished product of a thermo roll is manufactured using a thermo roll.

CROSS REFERENCES TO RELATED APPLICATIONS

This application is a U.S. national stage application of InternationalApp. No. PCT/FI2004/000503, filed Aug. 30, 2004, and claims priority onFI App. No. 20031230, filed Sep. 1, 2003; FI App. No. 20031232, filedSep. 1, 2003; FI App. No. 20031231; filed Sep. 1, 2003, FI App. No.20031233; filed Sep. 1, 2003; and FI App. No. 20031743, filed Nov. 28,2003, the disclosures of which are incorporated by reference herein.

STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSOREDRESEARCH AND DEVELOPMENT

Not applicable.

BACKGROUND OF THE INVENTION

The present invention relates to fibrous web machines, advantageously toapparatus for the treatment of a paper, board, pulp or equivalent web,such as paper, board or pulp machines and finishing devices associatedwith them, such as calenders.

The present invention relates to a heatable and/or coolable roll, i.e. athermo roll, of a fibrous web machine for the treatment of a fibrousweb, for example, for pressing and/or calendering the fibrous web incontact, i.e. in a nip, between the thermo roll and a backing memberwhich is in contact with the thermo roll or for drying or cooling thefibrous web on the shell surface of the thermo roll.

The present invention also relates to a thermo roll in an apparatus forthe treatment of a fibrous web, which thermo roll includes a rotatingcylindrical shell, a body formed of one or more parts and arrangedinside the shell, at least one heat transfer medium flow passage definedby the inner surface of the shell and the outer surface of the body, aheat transfer medium, heat transfer medium conveying means for passingthe heat transfer medium into the flow passage and for removing the heattransfer medium from it, as well as means for controlling the flow ofthe heat transfer medium to heat and/or to cool the shell by means ofthe heat transfer medium.

The present invention further relates to methods for using a thermo rollintended for the treatment of a fibrous web and including a shell thatcomprises at least two material layers, which thermo roll or the shellof which thermo roll as been provided with heat transfer means forheating and/or cooling the shell of the thermo roll, advantageously bymeans of a heat transfer medium.

The present invention further relates to methods for manufacturing athermo roll intended for the treatment of a fibrous web and including ashell that comprises at least two material layers, which thermo roll orthe shell of which thermo roll is provided with heat transfer means forheating and/or cooling the shell of the thermo roll, advantageously bymeans of a heat transfer medium.

The present invention also relates to thermo rolls intended for thetreatment of a fibrous web and including a shell that comprises at leasttwo material layers, which thermo roll or the shell of which thermo rollhas been provided with heat transfer means for heating and/or coolingthe shell of the thermo roll, advantageously by means of a heat transfermedium.

The present invention also relates to a semi-finished product of athermo roll intended for the treatment of a fibrous web and including ashell that comprises at least two material layers, the shell of whichthermo roll has been provided with heat transfer means for heatingand/or cooling the shell of the thermo roll, advantageously by means ofa heat transfer medium.

The present invention also relates to a thermo roll for manufacturing,in particular for finishing, a low-gloss and smooth fibrous web, thethermo roll being for manufacturing a low-gloss fibrous web, inparticular for finishing by calendering in a device situated in afinishing line of a fibrous web machine, such as a multinip calender, asoft calender, a machine calender, a belt calender, a metal beltcalender or in some combination of said calendars.

It is known to manufacture thermo rolls entirely out of chilled castiron or steel. From FI patent 106054 it is known to manufacture a thermoroll entirely or partly by powder metallurgical means.

As prior art it is mentioned that today's heat transfer capacities ofthe thermo roll in calendering are 50-250 kW/m. In less demandingapplications it is possible to use chilled rolls, while demanding sitesof use require steel rolls.

Different coatings are known for control of wear and corrosion of thesurface of the thermo roll, such as thermally sprayed metallic orceramic coatings (Papermaking Science and Technology, Papermaking Part3, pages 80-81).

According to EP publication 598737-B2, the highest specific heattransfer capacity of chilled rolls is 22 kW/m². With respect totechnical strength, the limit of steel rolls is, however, higher, forexample, the specific heat transfer capacity of the Tokuden roll isabout 50 kW/m². The heat transfer capacity of steel rolls heated withoil is limited in practice by the availability of hot oil, thetemperature of which is today about 300° C.

In fibrous web machines, the thermo roll must have a high heat transfercapacity, in calendering, even as high as 150-400 kW/m. In the fibrousweb machines of the future, the heat transfer capacity required inimpulse drying with a long nip and with increasing running speeds isconsiderably higher, of the order of 500-800 kW/m. With ordinary rolldiameters, which are between 1.0 and 1.5 m, this means a specific heattransfer capacity of about 30-260 kW/m².

To improve heat transfer capacity, it has been proposed that the rollshell be formed of two or more material layers of different materials,so that at least one material layer conducts heat particularly well,such as copper, aluminum, a copper alloy, an aluminum alloy orequivalent, advantageous alloying elements being Sn, Zr and Cr. EPpublication 723612-B1 describes a roll shell formed of differentmaterial layers. The outermost material layer is a thin copper oraluminum layer that conducts heat particularly well and the innerload-bearing base is made of steel or the like. It has been furtherproposed, as appears from EP publication 597814, that heat transferpassages conducting a heat transfer medium be arranged in the roll shellof a press section roll.

FI patent 106054 proposes the manufacture of a thermo roll out of two ormore layers, in which the thermal conductivity of an outer layer ishigher than the thermal conductivity of an inner layer. Further, saidpatent proposes a powder metallurgical manufacturing method.

The prior art is characterized in

-   -   that the roll or the load-bearing base of the roll is composed        of steel or equivalent, whose heat transfer properties are not        the best possible (typically, the thermal conductivity of the        material λ<60 W/mK), and    -   that in order to improve the heat transfer properties of the        roll, the shell of the roll is provided with a material layer        that conducts heat well and/or with heat transfer passages, so        that the structure of the roll is technically complex and, thus,        expensive, and    -   that the heat transfer passages are situated in the roll shell        at a distance of about 40-80 mm from the outer surface, so that        with the materials used today a great temperature difference        (ΔT) is created in the roll shell, which leads to a high oil        temperature at high operating capacities.

SUMMARY OF THE INVENTION

In accordance with one aspect of one embodiment of the presentinvention, an aim is to reduce the weaknesses associated with the priorart.

In accordance with another aspect of another embodiment of the presentinvention, an aim is to provide a novel roll shell to make the technicalstructure of the roll less complex and to improve the heat transferproperties of the roll.

These aims are achieved by the thermo roll in accordance with theinvention, which thermo roll is generally characterized in that exceptfor an optional coating and/or surface treatment layer, the shell of thethermo roll is of one metal material which conducts heat particularlywell and whose thermal conductivity λ>70 W/mK.

In accordance with one embodiment of the invention, the metal materialof the shell is copper or aluminum or the like. In accordance withanother embodiment of the invention, the metal material of the shell isa copper or aluminum alloy or composition metal. Advantageous copper andaluminum alloys or composition metals can be produced by alloying, forexample, Sn, Cr and/or Zr with copper or aluminum. By this means it ispossible to produce copper and aluminum alloys or composition metalswhich are sufficiently strong and enable various pressing andcalendering applications of low surface pressure. A materialparticularly suitable for the material of the shell is CuCrZr(copper-chrome-zirconium), the physical values typical of this being:density 8-10 g/cm³, thermal conductivity 300-350 W/mK and elasticmodulus 100-150 GPa.

On the metallic material layer of the shell of the thermo roll, whichlayer is of one metal, there may be optionally a coating and/or surfacetreatment layer improving the wear resistance of the roll, such as agraphite coating, a metallic or ceramic hardcoating, so that the thermoroll is a coated and/or surface-treated metallic thermo roll.

The thermo roll may be an uncoated and/or non-surface-treated metallicthermo roll.

The thermo roll may have a center passage or bore for heating and/orcooling the thermo roll.

The thermo roll may have peripheral passages or bores for heating and/orcooling the thermo roll.

The thermo roll may be a cooling roll of a fibrous web.

Induction heaters may be placed inside and/or outside the shell of thethermo roll for heating the thermo roll.

The thermo roll may be a roll of a multiroll calender, a roll of a softcalender, a roll of a long nip calender, a roll of a shoe calender, aroll of a belt calender, a roll of a metal belt calender, a dryingcylinder, a thermo roll in a press of a fibrous web machine and/or athermo roll in a coating section.

The heat transfer capacity of the thermo roll may be in a range of150-400 kW/m.

When a press dryer and a long nip are associated with the thermo roll, aheat transfer capacity may be achieved which is in a range of 150-800kW/m.

The specific heat transfer capacity of the thermo roll may be in a rangeof 24-320 kW/m².

As stated above, on the metal shell made of one metal there can beoptionally a coating or a surface treatment, such as a graphite coating,a metallic or ceramic hardcoating, which improves the wear resistance ofthe roll and the thickness of which is typically 5 mm at the most. Inparticular, it is possible to use a conventional hardcoating, whosethickness is 0.01-2 mm. The thermo roll in accordance with the inventionis then a coated or surface-treated metallic thermo roll with high heattransfer capacity. Without coating or surface treatment, the thermo rollis an uncoated or non-surface-treated metallic thermo roll with highheat transfer capacity.

The thermo roll in accordance with the invention can be heated andcooled using known methods by means of a central center passage or bymeans of flow passages provided in the shell of the thermo roll. Heatingis also possible by internal and/or external induction. The inductionheating technique of the Tokuden type is particularly suitable forheating. Thus, the thermo roll in accordance with the present inventiondoes not place restrictions on the selection of the heating arrangement.

Since the shell of the roll in accordance with the invention is made ofone material that conducts heat well, the thickness of the shell can bemade thicker and, thus, the heat transfer distance can be made longerthan that of the conventional rolls, while maintaining the same heattransfer capacity. By this means, the system of flow passages of theheat transfer medium in the roll becomes less complex and peripheralpassages are not necessarily even needed, which matters substantiallysimplify the roll arrangement.

As sites of application of the thermo roll of the invention may bementioned in particular a calender situated in the finishing section ofa paper and board machine line, in which calender the desired finalproperties of paper are achieved by pressing the web by means of aheated roll. The sites of application include known calenderarrangements, such as a multiroll calender, a long nip calender, a beltcalender and a soft calender, and in particular a shoe calender andvarious variants of a metal belt calender which require that thermorolls have high heat transfer capacity.

The other sites where the thermo roll in accordance with the inventioncan be applied include the presses used in the press section of thepaper and board machine, in particular the hot press or the so-calledimpulse press used for producing efficient dewatering. Further, as othersites where the thermo roll in accordance with the invention can beapplied in a fibrous web machine can be mentioned the drying cylindersused in the dryer section and the thermo roll of the coating section, inparticular in the process of attachment of a dry coating.

The heating and cooling delay of the thermo roll in accordance with theinvention is short, so that the thermo roll in accordance with theinvention is particularly suitable for fibrous web machines with a highrunning speed and/or for fibrous web machines in which there aresubstantial moisture variations in the fibrous web either in the runningi.e. MD direction of the fibrous web and/or in the cross direction i.e.CD direction with respect to the running direction of the fibrous web,or substantial needs for adjusting the heating control of the roll.

The present invention thus also relates to a thermo roll in an apparatusfor the treatment of a fibrous web, which thermo roll includes arotating cylindrical shell, a body formed of one or more parts andarranged inside the shell, at least one heat transfer medium flowpassage defined by the inner surface of the shell and the outer surfaceof the body, a heat transfer medium, heat transfer medium conveyingmeans for passing the heat transfer medium into the flow passage and forremoving the heat transfer medium from it, as well as means forcontrolling the flow of the heat transfer medium to heat and/or to coolthe shell by means of the heat transfer medium.

This kind of thermo roll is known, for example, from U.S. Pat. Nos.4,658,486 and 6,289,797.

In general, so-called peripherally bored tubular rolls made of steel orcast iron are used as thermo rolls, the heat transfer medium flowing inthe rolls being either water or oil. Typically, the peripheral bores arepassages drilled in the roll shell in the axial direction and placed ata distance of about 50-70 mm from the outer surface of the roll. Aproblem with peripherally drilled rolls is the complicated manufacturingprocess, primarily peripheral drilling, which is expensive and difficultto perform accurately such that the distance of the passages from thesurface would be constant and the distribution of heat would be even. Itis also typical of peripheral bores that the heat transfer mediumflowing in the passages tends to cool while flowing, so that the heatingeffect occurring in the shell is uneven in the axial direction of theroll. To avoid this, a displacement part supported on the walls of thepassage is sometimes placed in the peripheral bores in an attempt toaccelerate the flow, thus improving heat transfer at the cooler end ofthe flow passage. Further, oil can also be conducted in oppositedirections in different peripheral passages, which evens out the overallheating effect in the axial direction. One known problem withperipherally bored rolls is also that periodic variations in thecircumferential direction tend to be created in the temperaturedistribution of the roll shell according to the placement of bores,which leads to the fact that thermal expansions cause periodicvariations in the outside diameter of the roll, a so-called undulationeffect, which in turn may cause barring problems.

A center passage construction of the thermo roll is also known in whichthe volume of the center part of a tubular roll, i.e. the so-calledcenter passage, serves as a flow passage. To enhance the heat transferof the flows in the center passage and to assure the axial evenness ofheat transfer, it is also known to use a displacement part which issupported on the inner surface of the shell and which causes the flow topass as a gap flow in the axial direction. The gap flow is sought to bearranged such that with a decreasing cross sectional area of the flowpassage, the flow suitably accelerates causing heat transfer to beenhanced to a suitable extent. It shall be noted that when the centerpassage arrangement is used, there occurs no periodic “undulationdisturbance” typical of peripherally bored rolls.

The above-mentioned thermo roll constructions do not, as such, make itpossible to profile a fibrous web in the CD direction, i.e. in the crossdirection of the fibrous web, using the oil heating arrangementdescribed above. Typically, in connection with the manufacture andfinishing of a fibrous web there occurs a need for profiling both inrespect of the thickness i.e. caliper of the web and in the case ofprinting papers, in addition, also in respect of surface properties, inparticular gloss. In these situations, an external actuating means mustbe used for the CD direction profiling of the web, such an actuatingmeans being, for example, air blowing affecting locally the surfacetemperature of the thermo roll or a profiling induction heating means oranother equivalent actuating means.

Further, it may be mentioned that the heat transfer capacity of theabove-mentioned thermo roll constructions is too limited in view oftoday's production processes, mainly because of the limited temperatureof oil (typically below 350° C.) and the low thermal conductivity of theshell material of the thermo roll.

Previously, structural improvements of the shell of the thermo roll havebeen proposed for improving heat transfer. In accordance with oneproposal, the shell of the thermo roll is provided in the radialdirection with at least one material layer made of a metal that conductsheat well, such as copper or aluminum, or of an alloy, such as a copperof aluminum alloy or composition metal (e.g. CuCrZr) or of another metalor alloy that conducts heat well. This kind of thermo roll of improvedthermal conductivity is then suitable for demanding processes, such aslong nip calendering and belt calendering, in which connection therequired heat capacity is of the order of 200-300 kW/m, without thetemperature of oil having to be raised over the temperature range of300-350° C. In accordance with another proposal, the entire roll shellcan be manufactured of a material that conducts heat particularly well,such as the above-mentioned metals, so that a center bored roll witheven a relatively thick shell is suitable for said demanding processconditions. In accordance with a third proposal, the shell of the thermoroll can be manufactured by special manufacturing methods (such as bypowder metallurgical means) such that peripheral passages can beconstructed already in the manufacturing stage particularly close to theouter surface of the roll, so that the heat transfer distance becomesshort.

A general object of the present invention is to remedy theabove-mentioned drawbacks, its special object being to provide a simpleand efficient heat transfer arrangement for a thermo roll, in particularby the following means:

-   -   by improving the functioning of the heat transfer flow of the        center passage construction known to be simple such that the        center passage construction is suitable for demanding processes,        such as impulse drying and calendering, in particular for long        nip, belt and metal belt calendering, in which a peripherally        bored roll can be replaced with a roll in accordance with the        invention,    -   by providing a simple way of profiling in the CD direction        without external actuating means that take up much space, and    -   by applying the tried and inexpensive oil heating technique.

By the thermo roll is meant in this description of the invention and inthe claims a roll which is intended for the treatment of a fibrous webin a fibrous web machine, such as for the pressing, drying, coating orcalendering or cooling of a fibrous web, which roll can be heated and/orcooled by means of a heat transfer medium. The surface temperature ofthe shell part, or more briefly the shell, of the thermo roll varies,depending on the nature of the treatment process of the fibrous web,typically in a range of 20-350° C. Since in order to increaseproductivity it has been necessary to constantly increase the runningspeeds of the treatment equipment of the fibrous web, a need has arisento improve the heat transfer capacity from the thermo roll to thefibrous web.

In accordance with one advantageous aspect of a preferred embodiment ofthe present invention, an object is a novel and inventive constructionof the heat transfer means, such as flow passages and flow-guidingmembers, and the roll shell itself in a thermo roll such that the highheating and/or cooling capacity required also by efficient processes canbe produced by means of a simple and advantageous technical arrangementthat takes up little space.

In accordance with a second aspect of the preferred embodiment of thepresent invention, it is an object to provide a novel and inventiveconstruction for arranging the flow of a heat transfer medium in thecenter passage of a center bored thermo roll to increase the flowvelocity of the heat transfer medium and to prevent plug flow so thatthe center drilled roll may be used in demanding applications.

In accordance with a third aspect of the preferred embodiment of thepresent invention, it is an object to provide in the cross direction,i.e. CD direction, of the fibrous web a profiling effect on the fibrousweb by means of the flow of the heat transfer medium.

In accordance with a fourth aspect of the preferred embodiment of thepresent invention, an object is the use of the thermo roll in accordancewith the invention in applications that require a large heat transfer,such as, for example, calendering, in particular long nip, belt andmetal belt calendering, wet pressing, coating, in particular the processfor attaching dry coating, and impulse drying.

These objects are achieved by means of the present invention, thecharacteristic features of which are defined in the appended set ofclaims.

The invention is generally based on the novel and inventive basic ideathat inlets and outlets, respectively, of the heat transfer medium areconnected to the heat transfer medium conveying means of the thermo rollsuch that the heat transfer medium can be supplied into the flow passageand removed from the flow passage at more than one axial position of thethermo roll.

In accordance with one embodiment of the invention, a speed differenceis arranged between the wall surfaces of the shell and the body toenhance the flow of the heat transfer medium.

In accordance with one embodiment of the invention, the body of thethermo roll is non-revolving.

In accordance with one embodiment of the invention, in at least one flowpassage, the height of the flow passage, i.e. the gap distance in a flowgap, or the length of the flow gap in the flow direction is adjustableat at least one point over the axial length of the roll to profile thetemperature of the shell in the axial direction.

In accordance with one embodiment of the invention, the means forcontrolling the heat transfer medium are movable in the radial directionor their shape can be adjusted in said direction to adjust the gapdistance in the flow gap.

In accordance with one embodiment of the invention, the means forcontrolling the heat transfer medium are movable in the axial directionor in the circumferential direction or their size and shape can bechanged in said directions to adjust the gap distance in the flow gapwithin a desired range.

In accordance with one embodiment of the invention, the means forcontrolling the heat transfer medium are formed of a throttling ordisplacement part which acts in the flow passage and which is movabletowards the inner surface of the shell or away from the inner surface ofthe shell.

In accordance with one embodiment of the invention, the body of thethermo roll is adjustable in shape or size.

In accordance with one embodiment of the invention, the gap distance inthe flow gap is about 1-50 mm, advantageously about 5-25 mm.

In accordance with one embodiment of the invention, a throttling meanslimiting the flow in the gap is arranged in the flow passage between theinlets and the outlets of the heat transfer medium. In accordance withone embodiment, this throttling means is adjustable.

A speed difference may have been arranged between the wall surfaces ofthe flow passage, which speed difference produces a pumping effect inthe heat transfer medium.

In accordance with one embodiment of the invention, the flow velocityand the flow quantity in the system of distribution passages supplyingthe heat transfer medium to the flow passage are adjustable in aposition-specific manner with respect to the axial direction of theroll.

In accordance with one embodiment of the invention, the thermo rollcomprises, in the area between the inner surface of the shell and theouter surface of the body, means for controlling the flow velocity inthe flow passage of the heat transfer medium to control the temperatureof the shell or the thermal expansions of the shell over the entirelength of the thermo roll either evenly or in a profiled manner.

In accordance with one embodiment of the invention, the temperature ofthe heat transfer medium in the system of distribution passagessupplying the heat transfer medium to the flow passage is adjustable ina position-specific manner with respect to the axial direction of theroll.

In accordance with one embodiment of the invention, the material of theshell is a metal material that conducts heat particularly well, such ascopper, tin, aluminum, zinc, chrome, zirconium or an equivalent metalmaterial that conducts heat well or an alloy or a composition metalformed of at least two of these materials. The metal material alloy isCuCrZr in accordance with one embodiment.

In accordance with one embodiment of the invention, the material of theroll shell is mainly iron-based alloys, such as cast iron or steel.

In accordance with one embodiment of the invention, fixed support isarranged for the body disposed inside the shell of the thermo roll or acenter of mass eccentric with respect to the thermo roll is arranged inthe body to prevent free rotation of the body.

The use of the thermo roll in accordance with the invention enablescalendering, in particular long nip, belt and metal belt calendering,wet pressing, impulse drying and coating and cooling of a fibrous web inapplications that demand a large heat transfer.

In accordance with one embodiment of the invention, the flow gap of theflow passage, which is adjustable in length and/or height, causes theflow in the flow passage to be accelerated and the effect of heattransfer to be enhanced. An advantageous gap distance is in a range ofabout 1-50 mm, preferably in a range of about 5-25 mm. Further, byadjusting the height or length of the flow passage locally in an axialposition, it becomes possible to control the flow and/or the heattransfer of the heat transfer medium in a position-specific manner inthe axial direction for controlling the temperature distribution of theshell over the entire length of the thermo roll either evenly or byprofiling in a controlled manner. In that connection, it is advantageousthat in the inner body of the roll there are profiling blocks or flowguides, one of them being, for example, a projection part connected tothe body part and movable in the radial, circumferential or axialdirection. Such a profiling block forms, in one embodiment of theinvention, a movable throttling and/or displacement part of the flow ofthe heat transfer medium.

In accordance with one embodiment of the invention, the flow of the heattransfer medium is controlled in the flow passage by means of thethrottling or displacement part, by means of which the gap flow passageof the heat transfer medium can be made narrower and/or lower. Theforced flow occurring in the narrowed passage accelerates, with theresult that the boundary layer of the flow becomes thinner and the levelof turbulence increases, causing heat transfer from the heat transfermedium to the shell to be enhanced. In other words, heat transfer can becontrolled by accelerating and/or by throttling the flow of the heattransfer medium in the flow passage by means of the control means.

Since the rotary motion of the roll shell contributes to the flowing ofthe heat transfer medium in the flow gap in the rotation direction ofthe periphery of the thermo roll shell, and this flow tends further torotate the inner body of the roll, this effect is cancelled inaccordance with one embodiment of the invention either by arranging aneccentric center of mass in the roll body, in which case free rotationof the freely journalled roll body is prevented, or by means of fixedsupport of the roll body.

In accordance with one embodiment of the invention, the metal materialof the shell is advantageously copper, aluminum or an equivalent metalmaterial that conducts heat well or a metal material alloy orcomposition metal that conducts heat well. The shell can also be made ofa conventional material, such as cast iron, steel, or the like. Anadvantageous metal material alloy is, for example, a copper or aluminumalloy or composition metal, in which connection, for example, Cr, Sn, Zrare advantageous alloy materials. One particularly advantageous metalmaterial alloy for the shell is CuCrZr.

When the shell conducts heat well and when the flow passage of the heattransfer medium comprises flow control means, traditional peripheralbores can be omitted from the thermo roll and the thermo roll inaccordance with the invention can be used in applications that require alarge heat transfer, said applications including, for example,calendering, in particular long nip, belt and metal belt calendering,wet pressing, impulse drying and process steps associated with coating.

In accordance with one advantageous embodiment of the invention, themain parts of the thermo roll are formed by the shell part of the rolland by the volume defined by the shell inside itself, which volumeserves as the flow passage of the heat transfer medium, in said volumebeing additionally placed one or more body parts separate from the shelland displacing and controlling the flow.

In accordance with one embodiment of the invention, a mutual speeddifference is arranged between the inner wall of the roll shell and thewall surfaces of the body parts inside the shell to enhance the flow ofthe heat transfer medium.

In the thermo roll in accordance with the invention, the flow of theheat transfer medium is arranged to pass in a flow gap between the shellpart and the body part, its direction being substantially in therotation direction of the periphery of the roll, i.e. in thecircumferential direction, thus differing from the traditional thermoroll in which the flow in the flow gap is mainly axial with respect tothe rotary motion of the roll. The flow in the circumferential directionof the roll provides the advantage that the oil which cools while itflows does not cause temperature differences in the axial direction ofthe thermo roll. Entry and exit openings of the flow medium, i.e. inletand outlet openings of the flow medium, are arranged in connection withthe center part, i.e. the body part, of the thermo roll substantiallyacross the entire width of the roll. In accordance with an advantageousembodiment of the invention, the flow is arranged to pass in a narrowflow gap over a significant part of the circumferential length of theroll, which is at least 20% of the circumferential length, so that theheight of the flow gap is 1-50 mm, advantageously 5-25 mm. The body partinside the shell is particularly advantageously substantiallynon-revolving, so that the flow of the heat transfer medium is arrangedto pass in the flow passage in a flow gap in which there is aconsiderable speed difference between the opposite walls, whereby astrong shear field is created in the flow, which benefits heat transfereffectively. In accordance with an advantageous embodiment, there is, inpractice, a speed difference of 20-30 m/s between the non-revolving bodyand the rotating shell, which means that the mean flow velocity of oilis 10-15 m/s with respect to both the stationary body part and therotating shell part. The flow velocity is thus significantly higher thanthat of the conventional peripheral passage and center passage flow (1-4m/s), which means greater turbulence and, thus, more efficient heattransfer. The energy required by the shear field and the turbulencecaused by the speed difference between the shell and the body isobtained from the rotary motion of the shell.

By arranging the oil inlet and outlet openings suitably and by disposinga suitable throttling or obstruction part in the area between said inletand outlet openings, the rotary motion of the shell produces asubstantial pumping effect in that portion between the outlet and inletopenings which is without said obstruction part, the energy for saidpumping effect being taken from the rotary motion of the shell. The needfor separate pumping is reduced and a high flow rate is achieved, whichmeans a large heat transfer capacity. In other words, the roll itselfserves as a pump. In addition, the pumping effect is enhanced withincreasing speed, precisely when more capacity is also needed.

The heat transfer properties of the shell of the thermo roll can bearranged to be effective by manufacturing the shell out of a materialthat conducts heat well (λ>70 W/m²K). The shell can be manufactured, forexample, of CuCrZr.

The heat transfer of the gap flow can be controlled, i.e. profiled, inthe CD direction in at least the following ways:

-   -   by profiling the temperature of the oil coming from the system        of distribution passages locally in the CD direction,    -   by profiling the flow quantity in the inlet or outlet passages,        for example, by changing the degree of throttling locally in the        CD direction by profiling blocks,    -   by controlling the height of the flow gap or the length of the        flow direction locally, for example, mechanically either by        moving or bending the body part of the roll or by adjusting the        shape or size of some part of the body part of the roll or by        regulating a separate actuating means connected to the body        part,    -   by controlling the viscosity of the heat transfer medium flowing        in the flow gap, for example, by means of a magnetic or electric        field in the case when a magneto- or electrorheological liquid        serves as the heat transfer medium, which liquid is described,        for example, in the publication WO 02064886.

The heat transfer arrangement can be combined with a conventionalperipherally drilled roll, in which connection it is possible to makeuse of both the peripheral bores and the center passage. Of course, theprior known profiling methods can also be used in connection with thermoroll intended in the invention.

The present invention then further relates to thermo rolls intended forthe treatment of a fibrous web, to methods for using a thermo rollintended for the treatment of a fibrous web, to methods formanufacturing a thermo roll intended for the treatment of a fibrous web,and to a semi-finished product of a thermo roll intended for thetreatment of a fibrous web and including a shell that comprises at leasttwo material layers, the shell of which thermo roll has been providedwith heat transfer means for heating and/or cooling the shell of thethermo roll, advantageously by means of a heat transfer medium.

Here, by the thermo rolls are meant heatable thermo rolls which are usedin fibrous web working devices used in the manufacture of a paper, pulpand board web and equivalent fibrous webs and whose shell ismulti-layered or layered. Such thermo rolls include, for example,

a roll in a press section, in particular a roll in an impulse press,

a drying cylinder in a dryer section,

a thermo roll in a machine calender, a so-called ‘breaker stack’calender, a soft calender, a multinip calender, a supercalender, a longnip calender and/or a belt calender or a metal belt calender or anothercalender of a fibrous web machine,

a thermo roll in a coating section of a fibrous web machine.

By the multi-layered or layered thermo roll is meant here a thermo rollshell structure that comprises material layers which are visually,physically, chemically or metallurgically distinguishable or separablefrom one another. Each material layer has its own individual materialproperties, which may be different from those of an adjacent layer. Bythe layer of the shell of the thermo roll is meant each layer of theshell of the thermo roll or part of the shell material which is alayered whole in the sense of the manufacturing technique, the materialproperties of which layered whole can be the same as those of the layermade by a manufacturing technique and situated on its inner or outerside.

Two principal objects of the operation of the thermo roll are totransfer enough heat to the fibrous web and to serve as a supportsurface for the fibrous web treated in the fibrous web machine.

Oil heating has been most commonly used as heating systems in thermorolls, with heated oil flowing in heat transfer medium flow passageswhich are situated in the shell of the thermo roll and which are mostoften formed of peripheral bores situated in the surface part of thethermo roll shell. Water and steam are also other traditional heattransfer mediums. The center passage of the thermo roll, i.e. a passagedrilled in the center line, or a hollow inner part of the thermo rollhas also been used as a flow passage for the heat transfer medium.

In addition to the foregoing, it is known to use heating accomplished bymeans of electric resistors, and induction heating from outside. Thethermo roll has also been heated merely by induction heating frominside. Such a thermo roll is, for example, the Tokuden roll. In theTokuden roll, a steel shell rotates around a fixed shaft provided withintegrated induction coils. Passages partly filled with a liquid arearranged in the rotating steel shell to even out the temperaturedistribution.

Either chilled cast iron or steel has been mainly used as the shellmaterial of the prior art thermo rolls, so that the shell of the entirethermo roll is thermally, in principle, of one and the same material.Today's thermo rolls are mainly peripherally bored chilled or steelrolls.

In a multi-layered chilled roll

an outer layer typically having a thickness of about 10-30 mm is of castiron, advantageously of “chill cast” iron, with thermal conductivity Ain a range of 20-25 W/mK,

under this there is an intermediate layer, a so-called “mottle” layer,whose thickness is typically about 20-30 mm, with λ in a range of 20-50W/mK, and

an inner part, i.e. the innermost layer, is typically of so-called greycast with thermal conductivity λ in a range of about 45-60 W/mK.

As a general rule, in known chilled rolls with a multi-layered shell,thermal conductivity thus decreases towards the outside. In steel rolls,the effective thermal conductivity λ, i.e. the effective mean value ofthermal conductivity, across the shell is in a range of about 20-40 W/mKdepending on the material.

Peripheral bores are generally at a distance of at least 55-65 mm fromthe outer surface, when measured from the center line. Thus, in chilledrolls they are, in practice, in the inner layer, i.e. in the grey cast,just below the intermediate layer. An important reason for this is thatthe boundary surface of a harder material is easy to drill. The numberand the diameter of bores vary. Typically, there are at least 20-50bores and their diameter is about 30-40 mm.

Poor strength, brittleness and non-uniformity of the material aresignificant problems with chilled rolls. Because of poor strength andbrittleness, the material does not withstand high tensile stresses,which may arise in intensive heating or cooling situations, whichinclude in particular error and emergency situations in the fibrous webprocess. For example, large heat transfer from inside the thermo rollthrough the outer surface to the web or from the web through the outersurface of the thermo roll into the thermo roll or the cooling/heatingof the thermo roll all cause great temperature differences in the shelland, in particular, in the boundary surface/surfaces of the materiallayers, so that different thermal stresses and thermal expansions causehigh shear forces, which may break the thermo roll. To avoid high shearforces, today's thermo rolls are cooled and heated slowly. This causesprocess delays, which increases production costs and productionproblems.

The non-uniformity and instability of the material of chilled rollscause problems in the dynamics of rotating rolls, so that vibrations,among other things, “barring” and balancing become problematic inparticular in multinip calenders. One reason is variations in thethickness of a single layer caused by the manufacturing technique, sothat the thermo roll bends when heated, i.e. because of asymmetricthermal expansion, a thermo roll that is well balanced as cold can bendand be poorly balanced at operating temperature. The instability of theinner layer, which is typically made of grey cast, in turn causes that,for example, the loads (bending) applied during transport and treatmentproduce small permanent deformations (deflections), which are seen onlyat the end-use site while the thermo roll rotates (vibrations).

To avoid the problems encountered in connection with chilled rolls,increasing use has been made of steel materials in the most demandingprocess situations. In that case, the advantages include, among otherthings, a better uniformity and stability and a considerably higherstrength of the material properties.

A problem associated with the manufacturing technique of both chilledrolls and steel rolls is that the peripheral bores are expensive anddifficult to make. A large number of bores are needed and they must beplaced relatively far from the surface of the thermo roll in order thatthe temperature distribution might be made sufficiently uniform and inorder that the locations and misalignments of bores should be of lesssignificance. It is difficult to drill longitudinal holes in the rollshell. It is usually necessary to drill two opposing holes fromdifferent directions. To speed up the evenness of heating and theheating and cooling steps, it would be advantageous to drill in theshell a larger number of flow passages than done today. So far it hasnot been possible to do so because of the demanding nature of thetechnique and because of costs.

In chilled rolls, the bores are placed in the soft inner layer, i.e.typically in the so-called grey cast. A high oil temperature inevitablyfollows from the long heat transfer distance between the bores and thesurface since the thermal conductivity of materials is relatively poorboth in chilled rolls and in steel rolls.

The diameter of the flow passages is generally constant over theirentire length. However, from the viewpoint of the evenness of heattransfer, the location and the cross-sectional area of the passages andthe circumferential length of their walls should, however, change in amanner corresponding to the change of heating oil temperature in thedirection of motion of the flow. In accordance with the prior art, thishas been achieved by changing the distance between the passage and theouter surface of the roll shell, by throttling the flow by means of aseparate throttling part, with the result that the cross-sectional areais reduced and the flow velocity increases, or by making the area of thewall larger by roughening, grooving, enlarging, etc. An often used wayof evening out differences in the heating temperature in the axialdirection is also to arrange the direction of the flow in adjacent flowpassages in different directions.

The placement of flow passages close to the outer surface of the thermoroll is advantageous because the heat transfer distance to the outersurface of the thermo roll then becomes short. In that case, however, itbecomes a problem that it is, however, necessary to use a relativelydense spacing of the flow passages in order to minimize the so-calledundulation phenomenon, i.e. in the case of a roll, the waviness of thethermo roll's roundness profile arising from local differences inthermal expansion caused by the heating passages of the thermo roll, andthe change of the temperature of the outer surface of the thermo rollvarying in an undulating manner.

The undulation phenomenon is known to induce roll vibrations andadversely affect the properties of the paper being treated in theprocess, which may be visible, among other things, as gloss andthickness differences in the paper.

A problem with known thermo rolls has also been the lack of sufficientlyquick cooling of the thermo roll. For example, in connection with rollreplacement, the thermo roll should be cooled quickly in order to avoidunnecessary process delays. A drawback of the heating arrangementsaccomplished by means of electricity has been the lack of a coolingsystem.

One big problem with the rolls heated from inside, such as the Tokudenrolls provided with internal induction heating, is the relatively highheat transfer resistance caused by a thick shell. Because of the lowthermal conductivity of the shell material, the temperature differencebetween the inner parts of the thermo roll and the outer surface of thethermo roll is great, readily of the order of 100° C. This is a specialproblem in this kind of Tokuden roll in which the inner surface of theroll is subjected to heating and the heat transfer distance to the outersurface is large. The heat transfer of the shell thus limits thespecific capacity density (per unit area) so that to achieve the sametotal capacity (nip capacity) it is necessary to use larger rolldiameters.

New calendering concepts require a large heat capacity transfer from thethermo roll to the fibrous web in the process, which means that thethermal properties of the materials of the thermo roll shell are ofgreat significance. Likewise, the material's resistance to thermalshocks is important.

A problem with the known thermo rolls of the above-mentioned type, whenusing new calendering methods, i.e. hot multinip calendering or long nipcalendering, is too slight a heat capacity transfer to a moistfast-moving web. Typical values are the desired surface temperature ofthe thermo roll shell of 200-250° C. and a heat capacity of 150-250 kW/min the shell of the thermo roll. The heat capacity can be even as muchas 400 kW/m if the process includes the moisturizing of the web withwater before the nip.

A problem with the prior art thermo roll arrangements is that the heatcapacity produced by mere oil heating is not able to keep the surfacetemperature of the thermo roll at a sufficiently high level with asensible oil temperature of <300-350° C. and with sensible rolldiameters of <1.5 m. To increase heat capacity, in the multinip calenderthere is no space for accommodating external induction heating, and theprice of external induction heating is not yet today competitive ascompared with oil heating.

In respect of material properties, such as elongation at fracture,tensile strength, thermal conductivity properties, a thermo roll of merechilled cast iron, which is, for example, of grey cast iron, is notsuitable for the transfer of a large heat capacity of theabove-mentioned kind because thermal stresses exceed the properties ofthe material. In the chill casting process, a certain number ofnon-uniform material properties are always created, which also causesdeflection errors when the thermo roll is heated/cooled as well asbalancing and vibration problems at high speeds of rotation. Thestrength properties of the material of the thermo roll made totally ofsteel again allow great temperature differences but the above-mentionedhighest sensible temperature of heating oil limits the heat capacitythat is achieved. In the known structures, great temperature differencesbetween oil and the achieved surface temperature of the thermo roll arelargely due to the poor heat transfer properties of the material of thethermo roll shell material and to a long heat transfer distance, whichlimit the density of heat flux.

Because of the high heat capacity demand of the process, the thermalconductivity of the thermo roll shall be substantially improved in orderthat it may be assured that enough heat capacity is transferred throughthe shell of the thermo roll to the nip and further to the fibrous webthat is treated. To enhance heat transfer, the heat transfer distancebetween the outer surface of the thermo roll shell and the heat transferarea shall also be reduced.

A general object of the present invention is to eliminate or at leastsubstantially reduce the above-mentioned drawbacks and weaknesses and toimprove the heat transfer properties of the thermo roll.

In accordance with one aspect of the present invention, a general objectis to provide a novel and inventive thermo roll whose operating and heattransfer characteristics are made more effective, in particular theobject is to improve

heat transfer from inside the thermo roll to the outer surface of thethermo roll,

heat transfer from the outer surface of the thermo roll into the thermoroll,

heating of the thermo roll shell, and

cooling of the thermo roll shell.

In accordance with an aspect of the present invention, a general objectis to provide a method for using a thermo roll intended for thetreatment of a fibrous web.

In accordance with an aspect of the present invention, a general objectis to provide a novel and inventive method for manufacturing a thermoroll.

In accordance with an aspect of the present invention, a general objectis to provide a novel and inventive semi-finished product of a thermoroll.

These objects are achieved by the present invention, the characteristicspecial features of which are defined in the appended set of claims.

In accordance with an embodiment of the invention, the thermo roll isgenerally characterized in that at least two different material layersare arranged, using a manufacturing technique, radially one within theother in the shell of the thermo roll, which material layers aremanufactured with respect to their manufacturing technique in differentstages or by different methods, and that there are heat transfer mediumflow passages confined by at least one of said material layers insideitself or situated in a boundary zone of said material layers.

The thermal conductivity of each material layer of the shell of thethermo roll may be in a range of 20-70 W/mK.

The material layers of the shell of the thermo roll may have beenmanufactured of a conventional material, such as a ferrous metal,advantageously steel or cast iron.

In accordance with an embodiment of the invention, the thermo roll isgenerally characterized in that material layers are arranged radiallyone within the other in the shell of the thermo roll, so that thethermal conductivities of at least two material layers are differentfrom one another, and that there are heat transfer medium flow passagesin at least one of said material layers or confined by at least one ofsaid material layers inside itself or situated in a boundary zone ofsaid material layers, the thermal conductivities of which materiallayers are different from one another.

At least one of said material layers, the thermal conductivities ofwhich are different from one another, may be a heat transfer layer whichis of a metal material that conducts heat particularly well, theeffective thermal conductivity of the thermo roll across the shell ofthe thermo roll being >70 W/mK.

The heat transfer layer of the thermo roll may be copper, brass, tin,aluminum, zinc, chrome, zirconium or a similar material that conductsheat particularly well or an alloy or a composition metal composed of atleast two of these materials.

The material alloy of the heat transfer layer may be CuCrZr.

A flow passage may have been arranged entirely or at least partly in thematerial layer of the shell of the thermo roll forming the heat transferlayer which conducts heat particularly well and is a surface layer ofthe shell and/or a material layer on the inner side of the surface layerof the shell.

A flow passage may have been arranged in a material layer of the shellof the thermo roll situated on the inner or on the outer side of theheat transfer layer.

The heat transfer layer may be the innermost material layer of the shellof the thermo roll.

The material layer of the shell of the thermo roll forming the heattransfer layer may have been arranged to extend in the axial directionof the thermo roll substantially only across the width of the web areaof the fibrous web such that substantially outside the web area theshell of the thermo roll is formed of a material that is thermally lessconductive than the heat transfer layer.

The heat transfer layer and the surface layer of the thermo roll may beof the same material.

The thermal conductivity of the material layers arranged in the shell ofthe thermo roll may change in a layer by layer fashion in the radialdirection of the thermo roll.

In respect of the thermal conductivities of the material layers of thethermo roll the heat transfer layer may have the best thermalconductivity.

The heat transfer layer may be on the inner side and/or on the outerside of a thermally less conductive material layer.

The layer thickness of the surface layer may be smaller than the layerthickness of the heat transfer layer, and that the heat transfer layermay be of a copper alloy, for example, CuCrZr, brass, tin, aluminum,zinc, chrome, zirconium, nickel, iron, steel or an alloy containingabove-mentioned metals, and that the surface layer may be of a materialselected from a group including steel, such as low carbon steel, ahardcoating, such as a chrome coating or a ceramic coating.

In the outer surface of some material layer situated on the inner sideof the surface layer there may be a recess or a groove, whosecross-sectional profile shape constitutes a portion of thecross-sectional profile of the flow passage, so that the recess or thegroove forms the flow passage together with the inner surface of theouter material layer.

In the inner surface of the surface layer and/or in the inner surface ofthe layer situated on the inner side of the surface layer there may be arecess or a groove, whose cross-sectional profile shape constitutes aportion of the cross-sectional profile of the flow passage, so that therecess or the groove forms the flow passage together with the outersurface of the inner material layer.

The thermo roll may comprise a system of heat transfer medium flowpassages such that the heat transfer distance between the outer surfaceof the surface layer of the shell and the system of flow passages of thethermo roll has been arranged to be short such that at least some of theflow passages have been placed, as measured from their center line,advantageously at a distance of 50 mm at the most, more advantageouslyat a distance of 10-40 mm, from the outer surface of the thermo roll.

There may be a flow tube in the flow passage.

A heat capacity in a range of 100-300 kW/m, preferably in a range of200-250 kW/m, may be transferred from the thermo roll to the fibrous websuch that the temperature of the heat transfer medium remains below 350°C.

The thermo roll may be intended for different pressing and calenderingapplications of low surface pressure.

A first method for using a thermo roll according to the invention isgenerally characterized in that from a thermo roll whose shell comprisesat least two different material layers which are arranged, using amanufacturing technique, radially one within the other, which materiallayers have been manufactured with respect to their manufacturingtechnique in different stages or by different methods, a system of heattransfer medium flow passages being placed in at least one of saidmaterial layers or confined by at least one of said material layersinside itself or situated in a boundary zone of said material layers, aheat capacity in a range of 100-300 kW/m, preferably in a range of200-250 kW/m, is transferred to the fibrous web such that thetemperature of the heat transfer medium is kept <350° C.

A second method for using a thermo roll according to the invention isgenerally characterized in that from a thermo roll whose shell comprisesat least two material layers which are placed radially one within theother and which are different in their thermal conductivities, a systemof heat transfer medium flow passages being placed in at least one ofsaid material layers or confined by at least one of said material layersinside itself or situated in a boundary zone of said material layers, aheat capacity in a range of 100-300 kW/m, preferably in a range of200-250 kW/m, is transferred to the fibrous web such that thetemperature of the heat transfer medium is kept <350° C.

In said method during the heating or cooling of the thermo roll aseparate heat transfer passage system may be used in a material layerthat conducts less heat to even out the temperature difference insidethe thermo roll such that thermal stresses remain in a range that causesno fatigue in the structure.

A first method for manufacturing a thermo roll according to theinvention is generally characterized in that at least two materiallayers which are different in their manufacturing technique are arrangedradially one within the other in the shell of the thermo roll, whichmaterial layers are manufactured with respect to their manufacturingtechnique in different stages or by different methods, and that heattransfer medium flow passages are arranged to be confined by at leastone of said material layers inside itself or to be situated in aboundary zone of said material layers.

In the said method the material layers of the shell of the thermo rollmay be manufactured of a material whose thermal conductivity is in arange of 20-70 W/mK.

The material layers of the shell of the thermo roll may be manufacturedof a conventional material, such as a ferrous metal, advantageouslysteel or cast iron.

A second method for manufacturing a thermo roll according to theinvention is generally characterized in that different material layersare arranged in layers radially one within the other in the shell of thethermo roll, the thermal conductivities of at least two of said materiallayers being different from one another, and that heat transfer mediumflow passages are arranged in at least one of said material layers or tobe confined by at least one of said material layers inside itself or tobe situated in a boundary zone of said material layers.

At least one material layer of the thermo roll may be manufactured usinghot isostatic pressing (HIP) or by casting or by forging.

The shell of the thermo roll may be fixed or assembled by welding, forexample by friction stud welding, soldering, thermal contraction, bymeans of bolts, using an interlocking joint, by casting or using hotisostatic pressing (HIP).

The flow passages may be formed in the shell of the thermo roll bymachining, for example, by milling, drilling or forging, or by pressing,for example using hot isostatic pressing (HIP), or by etching.

A heat transfer layer made of a metal material that conducts heatparticularly well may be arranged to form at least one of said materiallayers, so that the effective thermal conductivity λ of the thermo rollacross the shell of the thermo roll is >70 W/mK.

The heat transfer layer may be made of copper, brass, tin, aluminum,zinc, chrome, zirconium or of a material having similar heat transferproperties or of an alloy or a composition metal composed of at leasttwo of these materials.

CuCrZr may be selected for the material alloy of the heat transferlayer.

The material layer of the shell of the thermo roll forming the heattransfer layer may be arranged to extend in the axial direction of thethermo roll substantially only across the web width of the fibrous websuch that substantially outside the web area the shell of the thermoroll is formed of a material that is thermally less conductive than theheat transfer layer.

The heat transfer layer and the surface layer of the thermo roll may beformed of the same material.

The material layers of the shell of the thermo roll may be formed of aniron-based metal, advantageously steel.

A system of heat transfer medium flow passages may be arranged in thethermo roll such that the heat transfer distance between the outersurface of the surface layer of the shell and the system of flowpassages of the thermo roll is arranged to be short such that at leastsome of the flow passages may be placed, measured at their center line,advantageously at a distance of 50 mm at the most, preferably at adistance of 10-40 mm from the outer surface of the thermo roll.

A flow passage may be arranged entirely or at least partly in thesurface layer of the shell of the thermo roll and/or entirely or atleast partly in the material layer on the inner side of the surfacelayer of the shell.

The inner surface and/or the outer surface of the material layerintended for the shell of the thermo roll may be provided with recessesor grooves, whose cross-sectional profile shapes constitute a portion ofthe cross-sectional profiles of the flow passages formed in the shell ofthe thermo roll, so that the recesses or the grooves form flow passagestogether with the inner surface of the outer material layer or with theouter surface of the inner material layer to receive the flow of theheat transfer medium.

The recess or the groove forming the flow passage of the thermo roll maybe filled in an earlier manufacturing stage with a soft material, forexample with copper, which is drilled open in a later manufacturingstage or drilled open in a full-size roll.

A flow tube may be placed in the flow passage.

A thermo roll according to an embodiment of the invention is generallycharacterized in that at least two material layers which are differentin their manufacturing technique have been arranged radially one withinthe other in the shell of the thermo roll, which material layers havebeen manufactured with respect to their manufacturing technique indifferent stages or by different methods, and that there are heattransfer medium flow passages confined by at least one of said materiallayers inside itself or situated in a boundary zone of said materiallayers.

The material layers of the shell of the thermo roll may have beenmanufactured of a material whose thermal conductivity is in a range of20-70 W/mK.

The material layers of the shell of the thermo roll may have beenmanufactured of a conventional material, such as a ferrous metal,advantageously steel or cast iron.

A thermo roll according to an embodiment of the invention is generallycharacterized in that material layers have been arranged in stages or inlayers radially one within the other in the shell of the thermo roll,the thermal conductivities of at least two of said material layers beingdifferent from one another, and that there are heat transfer medium flowpassages in at least one of said material layers or confined by at leastone of said material layers inside itself or situated in a boundary zoneof said material layers.

At least one of said material layers, the thermal conductivities ofwhich are different from one another, may be a heat transfer layer whichis of a metal material that conducts heat particularly well, theeffective thermal conductivity λ of the thermo roll across the shell ofthe thermo roll being >70 W/mK.

The heat transfer layer may be made of copper, brass, tin, aluminum,zinc, chrome, zirconium or a material having similar heat transferproperties or an alloy or a composition metal composed of at least twoof these materials.

The material alloy of the heat transfer layer may be CuCrZr.

A flow passage may have been arranged entirely or at least partly in thesurface layer of the shell of the thermo roll and/or entirely or atleast partly in the material layer on the inner side of the surfacelayer of the shell.

A flow passage may have been arranged in the material layer of the shellof the thermo roll situated on the inner side of the heat transferlayer.

The heat transfer layer may be the innermost material layer of the shellof the thermo roll.

In the outer surface of some material layer situated on the inner sideof the surface layer there may be a recess or a groove, whosecross-sectional profile shape constitutes a portion of thecross-sectional profile of the flow passage, so that the recess or thegroove forms a flow passage together with the inner surface of the outermaterial layer.

In the inner surface of the surface layer and/or in the inner surface ofthe layer on the inner side of the surface layer there may be a recessor a groove, whose cross-sectional profile shape constitutes a portionof the cross-sectional profile of the flow passage, so that the recessor the groove forms a flow passage together with the outer surface ofthe inner material layer.

The material layer of the shell of the thermo roll forming the heattransfer layer may have been arranged to extend in the axial directionof the thermo roll substantially only across the width of the web areaof the fibrous web such that substantially outside the web area theshell of the thermo roll is formed of a material that is thermally lessconductive than the heat transfer layer.

The heat transfer and the surface layer of the thermo roll may be of thesame material.

The thermal conductivity of the material layers arranged in the shell ofthe thermo roll may be different in a layer by layer fashion in theradial direction of the thermo roll.

In respect of the thermal conductivities of the material layers of thethermo roll the heat transfer layer may have the best thermalconductivity.

The heat transfer layer may be on the inner side and/or on the outerside of a thermally less conductive material layer.

The material layers of the shell of the thermo roll may be of aniron-based metal, advantageously steel.

The thermo roll may comprise a system of heat transfer medium flowpassages such that the heat transfer distance between the outer surfaceof the surface layer of the shell and the system of flow passages of thethermo roll has been arranged to be short such that at least some of theflow passages may have been placed, measured at their center line,advantageously at a distance of 50 mm at the most, preferably at adistance of 10-40 mm from the outer surface of the thermo roll.

A flow tube may be placed in the flow passage.

The layer thickness of the surface layer may be smaller than the layerthickness of the heat transfer layer, and the heat transfer layer may beof a copper alloy, for example, CuCrZr, brass, tin, aluminum, zinc,chrome, zirconium, nickel, iron, steel or an alloy containingabove-mentioned metals, and the surface layer may be of a materialselected from a group including steel, such as low carbon steel, ahardcoating, such as a chrome coating or a ceramic coating.

A heat capacity in a range of 100-300 kW/m, preferably in a range of200-250 kW/m, may be transferred from the thermo roll to the fibrous websuch that the temperature of the heat transfer medium remains below 350°C.

The thermo roll may be intended for different pressing, cooling andcalendering applications of low surface pressure.

A semi-finished product of the thermo roll according to the invention isgenerally characterized in that an inner surface and/or an outer surfaceof a material layer intended for the shell of the thermo roll isprovided with recesses or grooves, whose cross-sectional profile shapesconstitute a portion of the cross-sectional profiles of flow passages tobe formed in the shell of the thermo roll, so that the recesses or thegrooves form flow passages together with the inner surface of an outermaterial layer or with the outer surface of an inner material layer toreceive a heat transfer medium flow or heat transfer medium flow tubes.

In the semi-finished product the flow passage may have been formed byaxial drilling or by spiral machining, for example, by milling, whichmay be entirely in a material layer of the shell of the thermo rolland/or may open to the inner or outer surface of the a material layer.

The structure of the shell of the thermo roll in accordance with anembodiment of the invention is such that the properties of the material,in particular thermal conductivity and mechanical strength, are designedto change in a layer by layer fashion in the radial direction of thethermo roll to improve the operating characteristics of the thermo roll.Since it is generally not possible to achieve the optimum with respectto thermal conductivity and mechanical strength simultaneously with thesame material, in accordance with this arrangement of the invention amaterial having the best property in view of the whole is selected foreach individual layer in the radial periphery of the thermo roll.

In accordance with an embodiment of the invention, the material layerwith the best thermal conductivity is most preferably placed between thesystem of flow passages and the outer surface of the shell in an areathat is as large as possible to form a heat transfer layer. Thisprovides efficiency in heat transfer, so that the temperature betweenthe flowing medium, advantageously oil, and the surface becomes low.When selecting a combination of materials for different layers, strengthand thermal expansions and the stress state created in connection withthe use of the thermo roll have been taken into account as limitations.

A particularly essential feature of an embodiment of the invention isthe material layers which are arranged radially one within the other inthe shell of the thermo roll and of which, in accordance with oneembodiment, the thermal conductivity of at least two is different.

The invention also makes it possible to arrange the layers of the thermoroll shell such that thermal conductivity can be the same in differentlayers, so that the material of the layers of the shell which aredifferent in respect of the manufacturing technique is, for example,chemically of the same conventional material, for example,advantageously steel.

The flow passages of the heat transfer medium arranged in the shell orin the heat transfer layer of the shell of the thermo roll in accordancewith the invention can be, for example, heat transfer bores or heattransfer tubes that extend in the axial direction mainly parallel to thecenter axis of the thermo roll or that run spirally with respect to theaxis of the thermo roll. The flow passages of the heat transfer mediumcan also run in the shell of the thermo roll turning spirally around theaxial rotation axis of the thermo roll.

In the forming of some material layer and the flow passages of thethermo roll it is possible to use, as an advantageous manufacturingmethod, hot isostatic pressing, i.e. the HIP method, of which the term‘hot pressing’ is also used hereafter in this connection.

In accordance with an embodiment of the invention, it is advantageous toplace flow passages in the shell of the thermo roll already in themanufacturing stage, thus avoiding massive drillings of a full-sizethermo roll. However, the flow passages are not necessarily finishedimmediately directly in connection with the manufacture of the shell orsome layer of the shell of the thermo roll without chip removal but, forexample, in connection with hot pressing it is possible to leave in thelocations of the flow passages a guide groove or a tube or soft metalwhich is, for example, drilled open when the roll has been assembled.The drilling of a full-size thermo roll can be avoided by manufacturingthe thermo roll by assembling the thermo roll of several coaxial rollsections. In that case the flow tubes of the heat transfer medium canalso be drilled at an oblique angle with respect to the axial directionparallel to the rotation axis of the thermo roll to provide spirallyrunning heat transfer medium flow passages in the full-size thermo roll.

In accordance with an advantageous embodiment of the invention, the heattransfer distance between the outer surface of the thermo roll shell andthe heat transfer area of the thermo roll is short, and it is possibleto limit heat transfer more accurately to the web area and to limit heattransfer outside the web area.

A particularly essential feature of one embodiment of the invention isconstituted by layered wholes arranged in layers radially one within theother in the shell of the thermo roll, according to the first embodimentof which wholes at least two material layers which are different inrespect of their manufacturing technique have been arranged radially onewithin the other in the shell of the thermo roll, which material layershave been manufactured with respect to their manufacturing technique indifferent stages or by different methods, and there are heat transfermedium flow passages confined by at least one of said material layersinside itself or situated in a boundary zone of said material layers.The material of the layers of the shell which are different in respectof the manufacturing technique can then be, for example, chemically ofthe same conventional material, for example, advantageously steel.

The invention also makes it possible arrange the layers of the shell ofthe thermo roll in accordance with one embodiment in layers radially toform layered wholes one within the other, so that the thermalconductivities of at least two of the material layers are different fromone another, and there are heat transfer medium flow passages in atleast one of said material layers or confined by at least one of saidmaterial layers inside itself or situated in a boundary zone of saidmaterial layers.

In the surface of the thermo roll there can be a fairly thin materiallayer, for example, a steel shell which affords desired strength,toughness, hardness, wear resistance, surface quality or other similarproperties and which may have lower thermal conductivity than that ofthe material layer serving as the heat transfer layer. In accordancewith one embodiment of the invention, the material layer forming theouter surface of the roll shell of the thermo roll is sought to be keptthinner than the material layer serving as the heat transfer layer inorder that the overall thermal conductivity of the roll shall not belowered too much. Thus, the surface layer can be even very thin, forexample, a chrome-plated layer or another hardcoating or ceramic layerif the material layer serving as the heat transfer layer inside it issufficient in respect of its mechanical properties to withstand thestresses arising through nip load and the thermal stresses of the thermoroll in order that the possibly hard and brittle material layer formingthe surface shall stick. Of course, the thermo roll in accordance withthe invention can also be manufactured without the coating layer of theroll shell.

In the surface of the thermo roll there can be a fairly thin materiallayer, for example, a steel shell which affords desired strength,toughness, hardness, wear resistance, surface quality or other similarproperties and which may have lower thermal conductivity than that ofthe material layer on the inner side of the surface layer, whichmaterial layer can serve as a special heat transfer layer since it is inrespect of its material highly thermally conductive, but the thermalconductivity and/or the other material properties of the surface layerand the layer on the inner side of the surface layer can also besimilar. If the outer surface of the roll shell of the thermo roll isformed by a thermally less conductive material layer, it is sought to bekept thinner than the material layer serving as the heat transfer layerin order that the overall thermal conductivity of the roll shall not belowered too much.

With the thermo roll optimized in respect of its heat transferproperties in accordance with the invention, the working devices of thefibrous web making use of the thermo roll, in particular a calender,such as a multinip calender, a supercalender, a soft calender, a longnip calender and a belt calender or a metal belt calender, as well as amachine calender, a so-called “breaker stack” calender or an equivalentcalender in a drying or finishing section of a fibrous web machine, andin particular an impulse press in a press section, a drying cylinder ina dryer section, and devices in connection with coating, in particularin the dry coating fixing process, can be designed for high heatcapacities without needing to use other heating methods in addition tooil heating to raise the surface temperature of the thermo roll shelland to transfer desired heat capacity to the fibrous web that is beingtreated.

To the outer side or to the inner side of the layered wholes, i.e.layers, of the shell of the thermo roll, said wholes being layered inthe sense of their manufacturing technique, it is possible to attachanother layer of the same or similar material advantageously usingdifferent manufacturing techniques, when desired, in stages, forexample, one layer at a time, for example, by hot isostatic pressing.Such layered structure of the thermo roll allows the layers of the shellto be controlled in a layer by layer fashion. Thus, a material thatconducts heat well can be placed in the structure at a location where itis desirable to enhance heat transfer, a material that conducts heatpoorly can be possibly placed in the structure at a location where it isdesirable to retard heat transfer and, moreover, it becomes possible toplace flow passages close to the surface of the shell, so that inaccordance with one object of the invention the heat transfer distancecan be reduced between the outer surface of the shell of the thermo rolland the heat transfer area, with a view to enhancing the transfer ofheat capacity through the shell of the thermo roll to the nip andfurther to the fibrous web that is treated.

The present invention thus also relates to a thermo roll formanufacturing, in particular for finishing, a low-gloss and smoothfibrous web, the thermo roll being for manufacturing a low-gloss fibrousweb, in particular for finishing by calendering in a device situated ina finishing line of a fibrous web machine, such as a multinip calender,a soft calender, a machine calender, a belt calender, a metal beltcalender or in some combination of said calendars.

Matte paper and board products are low-gloss, smooth products which areoften used in applications where a very high level of quality isrequired, for example as printing papers, art papers and photographicpapers. An essential feature is low gloss, matte quality, of thesurface, which nevertheless allows a high-quality and glossy printingresult.

As known, high-quality matte paper can be manufactured by calenderingpaper by means of a porous and small-scale coarse roll provided with aceramic coating. A ceramic coating roll is described, for example, inthe published application FI 971542. One such ceramic coating is ValMattby its trade name.

Since the surface of the roll is porous/coarse, paper does not becomemore glazed although linear load or temperature is raised, but ratherthe opposite it may be thought that the matte quality of the surfacebecomes more marked. On the other hand, smoothness and density increase,which is also necessary from the viewpoint of the printing result.

If it is desirable to increase production rate, the linear load and thetemperature or the heat capacity of the calender must be increased inorder to achieve smoothness. At high speeds, the heat transfer capacityof the thermo roll becomes a problem, which limits running speed in manycalendering applications.

Different arrangements have been proposed to enhance heat transfer, oneof which arrangements is, for example, a metal belt calender comprisinga long heat transfer zone. FI patent application 20031230 discloses athermo roll for enhancing heat transfer, the shell of which thermo rollis manufactured of a material that conducts heat well and which maycomprise a ceramic coating. FI patent application 20031231 discloses athermo roll for enhancing heat transfer, the shell of which thermo rollis provided with flow passages, and in FI patent applications 20031232and 20031233 the shell of the thermo roll is manufactured of twodifferent material layers. FI patent application 990691 discloses athermo roll whose shell is manufactured using a powder metallurgicalmethod.

A general object of the present invention is to reduce the weaknessesassociated with the prior art and to provide a thermo roll with improvedheat transfer properties and to provide a method using the thermo roll,by means of which thermo roll and method it is possible to manufacturelow-gloss and smooth printing papers and board products advantageouslyand efficiently.

These objects are achieved by the present invention whose characteristicfeatures are defined in the appended set of claims.

The thermo roll according to the invention is mainly characterized inthat the thermo roll has been arranged in at least one nip whichcalenders the fibrous web and which is in the device situated in thefinishing line of the fibrous web machine, that the heat transfercapacity of the thermo roll is 100-400 kW/m, that the distance of heattransfer medium flow passages in a shell of the thermo roll from theouter surface of the shell is <55 mm, and/or that the parts of the shellof the thermo roll significant with respect to heat transfer have beenmanufactured of a material which conducts heat well and whose thermalconductivity λ>70 W/mK.

The material of the thermo roll shell which conducts heat well may havebeen selected from a group including copper, tin, aluminum, zinc,chrome, zirconium or an equivalent metal material that conducts heatwell or an alloy or a composition metal formed of at least two of thesematerials, such as CuCrZr.

The thermo roll may have been coated with a ceramic coating, such as theValMatt coating.

The shell of the thermo roll may have been manufactured at least partlyusing powder metallurgy.

The surface of the thermo roll may be porous and coarse in itsmicrostructure to produce a fibrous web of matte quality in calendering.

A method for manufacturing a low-gloss fibrous web, such as matte paperor matte board, in particular for finishing by calendering, in whichmethod the thermo roll according to any embodiment of the invention isused, is characterized in that the fibrous web is calendered by means ofthe thermo roll in at least one nip in a multinip calender or a softcalender or a machine calender or a belt calender or a metal beltcalender or in some combination of said calenders.

In the method the fibrous web may be calendered on the same calender assome other fibrous web grade such that said fibrous web is calendered byoperating some of the nips using a smaller number of nips than whencalendering other fibrous web grades, in particular glossy grades.

In the method the fibrous web may be calendered in a separate nip whichis situated in a finishing line and in which there is a thermo rollaccording to the invention, and which nip can be used or not used whencalendering other fibrous web grades, in particular glossy grades.

In the method the calendering of the fibrous web may be performed on anuncoated or coated fibrous web.

With respect to the other aspects, characteristic features andadvantages of the invention, reference is made to the dependent claimsof the set of claims and to the following special part of thedescription, which describes in detail, yet only by way of example, someembodiments of the invention considered to be advantageous and how theycan be carried out.

In the following, the invention will be described by way of example bymeans of some of its advantageous embodiments with reference to theappended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of an embodiment of an uncoated thermoroll in accordance with the invention.

FIG. 2 is a cross-sectional view of an embodiment of a coated thermoroll in accordance with the invention.

FIG. 3 is a cross-sectional view of an embodiment of an uncoated thermoroll provided with peripheral passages in accordance with the invention.

FIG. 4 is a cross-sectional view of an embodiment of a coated thermoroll provided with peripheral passages in accordance with the invention.

FIG. 5 shows a thermo roll provided with a center passage and with aninduction heater placed outside the shell in accordance with anembodiment of the invention.

FIG. 6 shows a thermo roll provided with a center passage and with aninduction heater placed inside the shell in accordance with anembodiment of the invention.

FIG. 7 is a longitudinal sectional view of an embodiment of a thermoroll in accordance with the invention.

FIG. 8 is a cross-section of the thermo roll shown in FIG. 7.

FIG. 9 is a cross-sectional view of a thermo roll in accordance withanother embodiment of the invention.

FIG. 10 illustrates layers and flow passages of a thermo roll shell thatcan be used in some embodiments of the invention.

FIG. 11 is a partial cross-sectional view of the grooved innermost layerof a thermo roll shell in accordance with a first advantageousembodiment of the invention.

FIG. 12 is a partial sectional view of the innermost layer of the shellshown in FIG. 11 and of a material layer that surrounds it and serves asa heat transfer layer.

FIG. 13 is a partial sectional view of the shell of the thermo rolloptimized in respect of its heat transfer properties in accordance withthe first embodiment of the invention and provided with flow passagesfor a heat transfer medium.

FIG. 14A shows a thermo roll assembled of parts and optimized in respectof its heat transfer properties in accordance with a second advantageousembodiment of the invention.

FIG. 14B shows flow passage shapes formed in the boundary surface of twomating parts.

FIG. 15 shows a thermo roll shell in accordance with a third embodimentof the invention.

FIG. 16 shows a thermo roll shell in accordance with a variant of thethird embodiment of the invention.

FIG. 17 shows an example diagram of the temperature distribution in theshell of the thermo roll in accordance with the first embodiment of theinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference is made to FIG. 1, which is a cross-sectional view of anembodiment of an uncoated thermo roll in accordance with the invention.

In the thermo roll of the embodiment shown in FIG. 1 there is a radiallycentral bore or passage 2 for a heat transfer medium and a thermo rollshell which defines the central passage 2 and is formed in its entiretyof a material layer 1 composed of one metal, the outer surface 4 of saidmaterial layer being, for the treatment of a fibrous web, in contactwith said fibrous web.

In accordance with the invention, the thermal conductivity of themetallic material layer 1 is particularly good, which means that thethermal conductivity λ of the material layer 1>70 W/mK. Because of sucha particularly good thermal conductivity, the roll has a high heattransfer capacity, even as high as 150-400 kW/m. It shall be noted,however, that in the fibrous web machines of the future, when an impulsedryer (see FIG. 5) and a long nip are associated with the thermo rolland when the running speeds of fibrous web machines increase, yetconsiderably higher heat transfer capacities, even as high as 500-800kW/m, will be needed. In an application in accordance with one exampleof the invention where diameter is in a range of 1.0-1.5 m, the specificheat transfer capacity is then in a range of 30-260 kW/m2.

Reference is made to FIG. 2, which is a cross-sectional view of anembodiment of a coated thermo roll in accordance with the invention.

In the embodiment of FIG. 2, the thermo roll has a hardcoating, whichimproves the wear resistance of the roll and which is of graphite or ametallic hardcoating or the like. The thickness of the hardcoating isbelow 5 mm, typically 0.01-2 mm.

In the thermo roll of the embodiment of FIG. 2 there is a radiallycentral bore or passage 2 for a heat transfer medium and a thermo rollshell which surrounds the central passage 2 and is formed by a materiallayer 1 composed of one metal and by a hardcoating placed on thematerial layer, the outer surface 5 of said hardcoating being, for thetreatment of a fibrous web, directly in contact with said fibrous web.

The center passage 2 of the thermo roll thus serves as a flow passagefor the heat transfer medium. This passage 2 can be provided with knowndevices that improve flow and heat transfer, such as a displacementpart, flow guides or by shaping the surface of the center passage 2suitably, for example, by roughening or grooving. The system of centerpassages can also be variable in the axial direction in its diameter or,more generally, in its cross-sectional flow area. It is generallynecessary to enhance and control the flow in order that the heat fluxpassing through the roll shell should be even in the axial direction (CDdirection).

In the embodiment of FIG. 2, in accordance with the invention, thethermal conductivity of the metallic material layer 1 is particularlygood, which means that the thermal conductivity λ of the material layer1>70 W/mK. Because of such a particularly good thermal conductivity, theroll has a high heat transfer capacity, even as high as 150-400 kW/m. Itshall be noted, however, that in the fibrous web machines of the future,when an impulse dryer (see FIG. 5) and a long nip are associated withthe thermo roll and when the running speeds of fibrous web machinesincrease, yet considerably higher heat transfer capacities, even as highas 500-800 kW/m, will be needed. In an application in accordance withone example of the invention where diameter is in a range of 1.0-1.5 m,the specific heat transfer capacity is then in a range of 30-260 kW/m².

Reference is made to FIG. 3, which is a cross-sectional view of anembodiment of an uncoated thermo roll provided with peripheral passagesin accordance with the invention.

In the thermo roll of the embodiment of FIG. 3 there is a radiallycentral bore or passage 2 for a heat transfer medium and a thermo rollshell which surrounds the central passage 2 and is formed in itsentirety of a material layer 1 composed of one metal, the outer surface4 of said material layer being, for the treatment of a fibrous web,directly in contact with said fibrous web.

In accordance with the invention, the thermal conductivity of themetallic material layer 1 is particularly good, which means that thethermal conductivity λ of the material layer 1>70 W/mK. Because of sucha particularly good thermal conductivity, the roll has a high heattransfer capacity, even as high as 150-400 kW/m. It shall be noted,however, that in the fibrous web machines of the future, when an impulsedryer (see FIG. 5) and a long nip are associated with the thermo rolland when the running speeds of fibrous web machines increase, yetconsiderably higher heat transfer capacities, even as high as 500-800kW/m, will be needed. In an application in accordance with an example ofthe invention where diameter is in a range of 1.0-1.5 m, the specificheat transfer capacity is then in a range of 30-260 kW/m².

To enhance the heat transfer properties, the material layer 1 of thethermo roll shell in the embodiment of FIG. 3 is provided withperipheral or shell passages 3 parallel to the axis of rotation ordeviating from the direction of the axis of rotation of the thermo roll,through which passages a heat transfer medium can be passed in additionto the central bore or passage 2.

The peripheral passages 3 in accordance with the embodiment of FIG. 3can be provided with devices that control flow and heat transfer, suchas displacement parts or flow guides or by shaping the inner surface ofthe shell passages 3 suitably. The passages 3 can also be variable inthe axial direction in their diameter or, more generally, in theircross-sectional flow area. It is generally necessary to enhance the flowin order that the heat flux passing obtained from the system of passagesshould be even in the axial direction (CD direction) of the roll.

The roll arrangements of FIGS. 3 and 4 can also be used so that the heattransfer medium is caused to flow only in the system of shell passages,as in the conventional thermo roll.

Reference is made to FIG. 4, which is a cross-sectional view of anembodiment of a coated thermo roll provided with peripheral passages inaccordance with the invention.

In the embodiment of FIG. 4, the thermo roll has a hardcoating 5, whichimproves the wear resistance of the roll and which is of graphite or ametallic or ceramic hardcoating or the like. The thickness of thehardcoating is below 5 mm, typically 0.01-2 mm.

In the thermo roll of the embodiment of FIG. 4 there is a radiallycentral bore or passage 2 for a heat transfer medium and a thermo rollshell which surrounds the central passage 2 and comprises a materiallayer 1 of one metal and the hardcoating placed on the material layer 1.For the treatment of a fibrous web, the outer surface 5 of thehardcoating is directly in contact with said fibrous web.

In the embodiment of FIG. 4, in accordance with the invention, thethermal conductivity of the metallic material layer 1 is particularlygood, which means that the thermal conductivity λ of the material layer1>70 W/mK. Because of such a particularly good thermal conductivity, theroll has a high heat transfer capacity, even as high as 150-400 kW/m. Itshall be noted, however, that in the fibrous web machines of the future,when an impulse dryer (see FIG. 5) and a long nip are associated withthe thermo roll and when the running speeds of fibrous web machinesincrease, yet considerably higher heat transfer capacities, even as highas 500-800 kW/m, will be needed. In an application in accordance with anexample of the invention where roll diameter is in a range of 1.0-1.5 m,the specific heat transfer capacity is then in a range of 30-260 kW/m².

To enhance the heat transfer properties, the metallic material layer 1of the thermo roll shell in the embodiment of FIG. 4 is provided withperipheral or shell passages 3 parallel to the axis of rotation ordeviating from the direction of the axis of rotation of the thermo roll,through which passages a heat transfer medium can be passed in additionto the central bore or passage 2.

The methods known in themselves can be used as methods of manufacturingthe shell part of the roll in accordance with the invention. The rollcan be manufactured either entirely or partly by powder metallurgicalmeans, as disclosed in FI patent 106054, using methods of castingtechnology, by cutting and forging methods.

The end and the shaft parts of the roll in accordance with the inventioncan be manufactured by the same known methods as those used for theshell part. The end parts can be manufactured of the same material asthe shell, but particularly advantageously they are manufactured out ofa metal that withstands loads well, such as steel.

To facilitate the machining of the peripheral passages 3, it isadvantageous that the thermo roll is composed of parts in the directionof the axis of rotation of the thermo roll, so that the thermo roll iscomposed of roll sections provided with axial or spirally extendingpassages formed, for example, by drilling, which passages formperipheral passages extending over the entire length or a selectablelength/part of the thermo roll when roll sections are disposed one afteranother. Particularly advantageously, the roll shell is manufactured bypowder metallurgical methods, as known, for example, from FI patent106054, in which case the system of peripheral passages can bemanufactured in connection with the manufacture of the shell.

Reference is made to FIG. 5, which shows a thermo roll provided with acenter passage and with an induction heater placed outside the shell inaccordance with an embodiment of the invention.

In the thermo roll of the embodiment of FIG. 5 there is a radiallycentral bore or passage 2 for a heat transfer medium and a thermo rollshell which surrounds the central passage 2 and is formed of a materiallayer 1 composed in its entirety of one metal, the outer surface 4 ofsaid material layer being, for the treatment of a fibrous web, directlyin contact with said fibrous web.

In the embodiment of FIG. 5, in accordance with the invention, thethermal conductivity of the metallic material layer 1 is particularlygood, which means that the thermal conductivity λ of the material layer1>70 W/mK. Because of such a particularly good thermal conductivity, theroll has a high heat transfer capacity, even as high as 150-400 kW/m. Itshall be noted, however, that in the fibrous web machines of the future,when an impulse dryer and a long nip are associated with the thermo rolland when the running speeds of fibrous web machines increase, yetconsiderably higher heat transfer capacities, even as high as 500-800kW/m, will be needed. In an application in accordance with an example ofthe invention where roll diameter is in a range of 1.0-1.5 m, thespecific heat transfer capacity is then in a range of 30-260 kW/m².

To enhance the heat transfer properties, the metallic material layer 1of the shell of the thermo roll in the embodiment of FIG. 5 is providedwith peripheral or shell passages 3 parallel to the axis of rotation ordeviating from the direction of the axis of rotation of the thermo roll,which passages may be arranged when needed, but not necessarily, andthrough which passages a heat transfer medium can be passed in additionto the central bore or passage 2. It is particularly advantageous to useperipheral passages for the cooling of the roll in connection withinduction heating when it is desirable to cool the roll shell quickly ina controlled manner, for example, when a service shutdown becomesnecessary. In addition, the thermo roll in accordance with theembodiment of FIG. 5 is provided with an external induction heater 6,which acts directly on the outer surface 4 of the thermo roll shell. Itshall be noted that the induction heater can also be disposed as aninternal induction heater of the thermo roll, for instance, as shown inFIG. 6, and that an induction heater/induction heaters can be disposedboth inside and outside the thermo roll.

To facilitate the machining of the peripheral passages 3, it isadvantageous that the thermo roll is composed of parts in the directionof the axis of rotation of the thermo roll, so that the thermo roll canbe composed of roll sections provided with axial or spiral passagesformed, for example, by drilling, which passages form peripheralpassages 3 extending over the entire length or a selectable length/partof the thermo roll when roll sections are disposed one after another.Advantageously, the roll shell can also be manufactured by powdermetallurgical means, in which case the flow medium passages can beformed in connection with the manufacture of the shell part.

Reference is made to FIG. 6, which shows a thermo roll provided with acenter passage and with an induction heater placed inside the shell inaccordance with an embodiment of the invention.

In the thermo roll of the embodiment of FIG. 6 there is a radiallycentral bore or passage 2 for a heat transfer medium and a thermo rollshell which surrounds the central passage 2 and is formed of a materiallayer 1 composed in its entirety of one metal, the outer surface 4 ofsaid material layer being, for the treatment of a fibrous web, directlyin contact with said fibrous web.

In the embodiment of FIG. 6, in accordance with the invention, thethermal conductivity of the metallic material layer 1 is particularlygood, which means that the thermal conductivity λ of the material layer1>70 W/mK. Because of such a particularly good thermal conductivity, theroll has a high heat transfer capacity, even as high as 150-400 kW/m. Itshall be noted, however, that in the fibrous web machines of the future,when an impulse dryer and a long nip are associated with the thermo rolland when the running speeds of fibrous web machines increase, yetconsiderably higher heat transfer capacities, even as high as 500-800kW/m, will be needed. In an application in accordance with an example ofthe invention where roll diameter is in a range of 1.0-1.5 m, thespecific heat transfer capacity is then in a range of 30-260 kW/m².

To enhance the heat transfer properties, the metallic material layer 1of the shell of the thermo roll in the embodiment of FIG. 6 is providedwith peripheral or shell passages 3 parallel to the axis of rotation ordeviating from the direction of the axis of rotation of the thermo roll,which passages may be arranged, as shown with broken lines in FIG. 6,when needed, but not necessarily arranged, and through which passages aheat transfer medium can be passed in addition to the central bore orpassage 2. It is particularly advantageous to use peripheral passagesfor the cooling of the roll in connection with induction heating when itis desirable to cool the roll shell quickly in a controlled manner, forexample, when a service shutdown becomes necessary. In addition, thethermo roll in accordance with the embodiment of FIG. 6 is provided withan internal induction heater 7, which acts on the shell of the thermoroll.

By way of example, it can be stated as specific values achievable in athermo roll of a calender in accordance with one exemplifyingembodiment: diameter advantageously 1500 mm, it can be e.g. 0.8-2 mshell thickness advantageously 100 mm, it can be 50-250 mm oiltemperature advantageously 300° C., it can be 100-400° C. roll surfacetemperature 250° C., it can be 100-380° C. heat capacity (to the web)250 kW/m, it can be 150-400 kW/m specific heat capacity 53 kW/m², it canbe 24-260 kW/m².

By way of example, it can be stated as specific values achievable in athermo roll of a press or an impulse press in accordance with anotherexemplifying embodiment: diameter advantageously 1500 mm, it can be e.g.0.8-2 m shell thickness advantageously 100 mm, it can be 50-250 mm oiltemperature 50-400° C. roll surface temperature 50-380° C. heat capacity(to the web) 150-800 kW/m specific heat capacity 24-320 kW/m².

The coating layer possibly used in the arrangement in accordance withthe invention can be, for example, a graphite, metal or ceramichardcoating, whose thickness is less than 5 mm, advantageously 0.01-2 mmand particularly advantageously 0.01-0.5 mm. The coating can be a hardchrome plating, a thermally sprayed coating (e.g. HVOF) or a coatingmade by a coating welding or laser coating method.

Reference is made to FIG. 7. The figure is a longitudinal sectional viewof a thermo roll in accordance with an embodiment of the invention. Thethermo roll includes a rotating shell 11 and a roll body 12, which isnon-revolving or rotating with a rotary motion at least substantiallydiffering from the speed of the rotary motion of the shell, so that theopposing surfaces defining a gap between the roll body 12 and the shell11 have a clear speed difference.

The thermo roll is provided with at least one flow passage 13 for a heattransfer medium between the roll body 12 and the shell 11 in thelongitudinal and circumferential direction of the roll body 12. The heattransfer medium is passed into the flow passage 13 from a distributionpassage/passages 16, whose inlet duct is at the end of the thermo roll,substantially simultaneously across the entire width of the thermo roll,and the heat transfer medium is removed from the flow passage into aheat transfer medium discharge passage 17, whose discharge duct is alsoat the end of the thermo roll, substantially simultaneously across theentire width of the thermo roll.

Reference is made to FIGS. 8 and 9. A heat transfer medium is passedinto the flow passage 13 by heat transfer medium supply means, whichinclude the distribution passage/passages 16 and an inlet/inlets 131connected to said distribution passage/passages, as well as thedischarge passage/passages 17 and an outlet/outlets 132 connected tosaid discharge passage/passages. The heat transfer medium is passed intothe flow passage 13 from at least one distribution passage 16 through atleast one heat transfer medium inlet 131 and the heat transfer medium isremoved from the flow passage 13 into at least one discharge passage 17through at least one heat transfer medium outlet 132. In the flowportion between the distribution passage/passages 16 and the flowpassage 13 and/or in the flow portion between the flow passage 13 andthe discharge passage/passages 17 there can be position-specific valvesor other similar throttling means in the axial direction of the thermoroll to control the flow and/or the temperature of the heat transfermedium in the flow passage 13. The shaping of the inlet 131 and/or theoutlet 132 is not essential to the present invention, but differentpassage designs can be used for connecting the flow passage 13 into flowcommunication with the distribution passage 16 and/or the dischargepassage 17.

It is characteristic of the invention that the flow of the heat transfermedium in the flow passage 13 can be controlled by a flow control means14. Since both the introduction and the removal of the hot heatingmedium takes place across the entire width of the roll, significanttemperature differences cannot be created in the axial direction of thethermo roll or it is at least easier to control temperature differences.In accordance with the arrangement of the invention, the flow of theheat transfer medium is arranged to pass in a flow gap 15 of the flowpassage 13 between the shell 11 and the body 12, in which flow gap therecan be a special displacement part, substantially in the circumferentialdirection of the roll instead of the flow passing in the flow gap in theaxial direction. The above-mentioned displacement part is, for example,the flow control means 14 shown in FIGS. 8 and 9. The flow in thecircumferential direction of the thermo roll provides the advantage thatthe oil that is cooling while it flows does not cause temperaturedifferences in the axial direction of the thermo roll. The entry andexit openings of the flow medium, i.e. the inlet openings 131 and theoutlet openings 132 of the flow medium, are arranged in connection withthe center part, i.e. the body 12, of the thermo roll, substantiallyacross the entire width of the thermo roll. Then, by controlling theflow and/or the temperature of the heat transfer medium in the flowpassage 13, the surface temperature of the shell 11 is controlled overthe entire length of the thermo roll either evenly or variably in acontrolled manner. This allows the fibrous web to be profiled by meansof the heating of the shell.

It shall be noted that the flow can also take place in the passage 13without the separate flow gap 15 being shaped by means of the separatecontrol means 14, in which case the flow system is determined merely bythe shaping of the walls of the body part 12 and the shell. The shapingof the walls, in particular in respect of the body part 12, can beselected in a manner satisfactory with respect to the flow, yetachieving a simple structure.

A profiling effect is achieved in accordance with one embodiment of theinvention by adjusting, in addition to the height of the flow passage13, i.e. the flow gap 15, also the length of the flow passage 13. Inaccordance with the invention, the flow gap 15 is generally definedbetween the inner surface of the shell 11 and the outer surface of thebody 12. In particular, the throttled part of the flow gap is formedbetween the shell 11 and the peripheral surface of the flow controlmeans 14 directed towards the shell 11. Since the control means 14 ismovable, it becomes possible to adjust the height of the flow gap 15,even to close it. It may be further contemplated that several controlmeans are arranged successively in the circumferential direction, ortheir throttling effect can be otherwise continued in the flowdirection, so that in the advantageous embodiments shown in FIGS. 8 and9, for the purpose of adjusting the height and/or the length of the flowgap 15, i.e. the flow in the gap, each control means 14 is formed by ablock element, i.e. profiling block 14, which is axiallyposition-specific and arranged in the roll body 12 and which manipulatesthe flow gap in the radial, circumferential or axial direction.Alternatively, the flow control means 14 of the heat transfer medium,which adjusts the height and/or the length of the flow gap 15 in theflow passage 13 of the heat transfer medium and which enables thefibrous web to the profiled, is, for example, an articulated projectionpart (not shown in the figures), i.e. a profiling part, arranged in theprofiling block and movable in the radial or circumferential direction.

Generally, the flow control means 14 of the heat transfer medium, i.e.the profiling part, which adjusts the height and/or length of the flowgap 15 in the flow passage 13 of the heat transfer medium and whichenables the fibrous web to the profiled, is a heat transfer medium flowthrottling and/or displacement part 14 which is movable or which changesits shape and by means of which at least the height of the flow gap 15of the flow passage 13 and/or the length of the flow passage 13 can beadjusted.

In an advantageous embodiment of the invention, the control of the flowof the heat transfer medium in the flow passage between the roll body 12and the shell 11 is accomplished by means of the throttling and/ordisplacement part 14. At least one throttling and/or displacement part14 is arranged in the flow passage successively both in the longitudinaland in the circumferential direction of the roll body 12. Eachthrottling and/or displacement part forms, in the radial directionbetween itself and the shell 11, one or more flow gaps 15, whose gapdistance is 1-50 mm, advantageously about 5-25 mm.

This gap distance as well as the length of the flow gap 15 aredimensioned, based on heat transfer calculations, to be sufficientlylong in the circumferential direction. Advantageously, the flow gap is,however, effective in a portion of over 20% of the length of the innercircumference. The function of the flow gap 15 is to accelerate the flowof the heat transfer medium so that a highly turbulent and mixing flowis created most advantageously, so that heat transfer from the gap flowto the inner surface of the roll shell 11 is efficient.

In accordance with the invention, it is recommendable in particular forproviding a turbulent and mixing flow that the profiling part form astraight-faced and acute-angled flow obstruction in the flow passage andthat the profile of the profiling part in the rotation direction of thethermo roll advantageously conform to the profile of the respective areain the opposing part of the flow gap 15. When the profiling part, i.e.the displacement part 14, is additionally movable in the flow passage 13in the radial and/or circumferential direction in accordance with theinvention, the gap distance of the flow gap 15 of the flow passage 13can be adjusted to generate a highly turbulent and mixing flow of theheat transfer medium, which enhances heat transfer from the heattransfer medium to the shell 11. The turbulence of the heat transfermedium flow can be enhanced further, for example, by at least partialgrooving, rough shaping or another kind of shaping of the inner surfaceof the shell 11 and/or the outer surface of the roll body 12, whichenhances the turbulence of the flow.

By arranging the inlet openings 131 and the outlet openings 132 of theheat transfer flow medium, for example, as shown in FIG. 8 and bydisposing a suitable throttling means or an obstruction part 18 betweenthese openings in the flow passage 13 such that the throttlingmeans/obstruction part 18 throttles a considerable part of the flowpassage 13 between the outer surface of the body 12 and the innersurface of the shell 11 (or closes it altogether), the relative rotarymotion of the shell 11 and the body 12 of the roll produces asignificant pumping effect, for which energy is taken from the rotarymotion of the shell 11. The throttling means 18, which is placed betweenthe inlet openings 131 and the outlet openings 132 and which can beadjustable, for example, movable in the radial direction of the roll,enhances the pressure difference in the flowing heat transfer medium.The need for separate pumping is reduced and a large through flow isachieved, which means a high heat transfer capacity. Thus, the thermoroll itself functions as a pump. Moreover, the pumping effect isenhanced with increasing speed, precisely when more capacity is alsoneeded.

Reference is made to FIG. 9. In many cases, the body 12 is fitted to bestationary. In the embodiment of the figure, the body 12 is rotating,for example, the body 12 is journalled at its ends. The free rotation ofthis kind of body 12 around the central axis of rotation PO is preventedor retarded by the center of mass PM arranged to be offset from thegeometric center axis PO of the body 12 in accordance with theinvention, i.e. the body 12 is eccentric.

A roll body 12 that is movable with respect to the thermo roll shell 11is also feasible. It is thus possible to adjust the height, i.e. the gapdistance, of the flow gap 15 of the flow passage 13, for example,mechanically either by moving the thermo roll body 12 with respect tothe shell 11 or by bending or by adjusting the shape or size of thethermo roll body 12 or by adjusting a separate actuating means connectedto the body 12. Further, the body part 12 which is inside the roll shelland which controls and displaces the flow can be as a whole or partlyadjustable in size or shape without needing a separate movable actuatingmember 14 for adjusting the gap distance in the flow passage.

Since the shell 11 rotates, this inner surface of the shell 11 “draws”some of the flow with it and since the center part 12 is totally oralmost static, the outer surface of the center part 12 slows down theflow. In that connection the flow velocity on the inner surface of theroll shell 11 and the flow velocity on the outer surface of the body 12differ substantially from each other, so that a very strong shear fieldis created in the gap flow of the flow gap 15 because of the greatdifferences in the flow velocities. Because of shear, the flow and heattransfer boundary layers become thinner and turbulence is generated moreeasily and heat transfer is improved. The flow of the heat transfermedium in the circumferential direction of the thermo roll in the flowgap 15 of the flow passage 13 tends to rotate the body 12 of the thermoroll, but this is cancelled in accordance with one embodiment of theinvention either by arranging an eccentric center of mass PM in the body12 or by means of fixed support of the body 12. In that case, the body12 journalled to be rotating remains non-revolving or rotatessubstantially more slowly than the shell 11.

FIGS. 10-17 illustrate a thermo roll 10′, 20′, 101′ which is used forthe treatment of a fibrous web and provided with heat transfer meansarranged inside a shell, thus being heatable or coolable on the inside,advantageously by means of a heat transfer medium. The shell of thethermo roll 10′, 20′, 101′ comprises at least two, in some embodimentsthree material layers 11′, 13′, 14′, 21′, 23′, 24′. The surface 14 a′,24 a′ of the outermost material layer is in contact with the fibrous webor a wire.

The thermo roll 10′, 20′, 101′ optimized in respect of its heat transferproperties in accordance with the invention is composed of one part orof several roll sections in the axial direction. At least two, in someembodiments advantageously three material layers 11′, 13′, 14′, 21′,23′, 24′ are arranged radially one within the other in the shell of thethermo roll 10′, 20′, 101′.

In accordance with a first embodiment of the invention, at least twodifferent material layers 11′, 13′, 14′, 21′, 23′, 24′ are arranged,using a manufacturing technique, radially one within the other in theshell of the thermo roll, which material layers have been manufacturedwith respect to their manufacturing technique in different stages or bydifferent methods, so that in accordance with one embodiment the thermalconductivity of each material layer in the shell of the thermo roll isin a range of 20-70 W/mK.

In accordance with a second embodiment of the invention, material layers11′, 13′, 14′, 21′, 23′, 24′ are arranged radially one within the otherin the shell of the thermo roll, the thermal conductivities of at leasttwo material layers being different from one another, so that inaccordance with one embodiment at least one of said material layers, thethermal conductivities of which are different from one another, is aheat transfer layer 13′, 23′, which is of a metal material that conductsheat particularly well, the effective thermal conductivity λ of thethermo roll across the shell of the thermo roll being >70 W/mK.

In addition, there are heat transfer medium flow passages 15′, 25′, 30′,151′, 152′ in at least one material layer 11′, 13′, 14′, 21′, 23′, 24′or in a material layer 11′, 13′, 14′, 21′, 23′, 24′ manufactured instages or in layers or assembled in stages or in layers or confined byat least one material layer inside itself or in a boundary zone of twomaterial layers.

In accordance with one advantageous embodiment of the invention, thethermo roll comprises a system of heat transfer medium flow passages15′, 25′, 151′, 152′ such that the heat transfer distance between theouter surface 14 a′, 24 a′ of the surface layer 14′, 24′ of the shelland the system of flow passages of the thermo roll is arranged to beshort such that at least some of the flow passages are placed, measuredat their center line, advantageously at a distance of 50 mm at the most,more advantageously at a distance of 10-40 mm from the outer surface ofthe thermo roll.

To enhance the even distribution of heat transfer and heat, the thermoroll 10′, 20′, 101′ comprises heat transfer means for heat transfer.

-   -   As shown in FIGS. 10-14B, the heat transfer means include a        material layer which is arranged between the inner layer 11′,        21′ of the thermo roll 10′, 20′ and the surface layer 14′, 24′        in contact with the fibrous web and which forms a heat transfer        layer 13′, 23′, which in accordance with one embodiment of the        invention is of a material whose thermal conductivity is higher        than the thermal conductivity of the inner layer 11′, 21′. In        accordance with one embodiment of the invention, the material of        the heat transfer layer 13′, 23′ is advantageously a material        that conducts heat particularly well and has an effective        thermal conductivity of >70 W/mK.    -   As shown in FIG. 15, the heat transfer means include a material        layer which is arranged to form the innermost layer of the        thermo roll 101′ and which forms a heat transfer layer 13′,        which in accordance with one embodiment of the invention is of a        material whose thermal conductivity is higher than the thermal        conductivity of the surface layer 14′ in contact with the        fibrous web and surrounding the heat transfer layer 13′. The        material of this material layer serving as the heat transfer        layer 13′ can be a material that conducts heat particularly well        and has an effective thermal conductivity of >70 W/mK.    -   As shown in FIG. 16, the heat transfer means include a material        layer of the thermo roll 101′, which material layer is thermally        more conductive and forms a heat transfer layer 13′ whose        material in accordance with one embodiment of the invention is a        material that conducts heat particularly well and has an        effective thermal conductivity of >70 W/mK, which material layer        is outside the innermost layer 11′ that is thermally less        conductive. The material of the innermost layer 11′ has been        selected optimally with respect to internal induction heating.

The layer 13′, 23′ that conducts heat particularly well can bemanufactured, for example, of copper or a copper alloy, such as, forexample, CuCrZr. As the material of the heat transfer layer 13′, 23′ itis also possible to use brass, tin, aluminum, zinc, chrome, zirconium,nickel, steel or the like. The material of the heat transfer layer canalso be an alloy or a composition metal containing above-mentionedmetals.

To enhance the even distribution of heat transfer and heat, the thermoroll 10′, 20′, 101′ comprises heat transfer means for heat transfer,which heat transfer means include those layers which affect heattransfer and are situated even partly between the heat transfer mediumflow passages and the outer surface of the thermo roll.

-   -   As shown in FIGS. 10-14B, the heat transfer means include a        material layer 13′, 23′ which is arranged between the inner        layer 11′, 21′ of the thermo roll 10′, 20′ and the surface layer        14′, 24′ in contact with the fibrous web and which in accordance        with one embodiment of the invention is of a material whose        thermal conductivity is higher than the thermal conductivity of        the inner layer 11′, 21′. In accordance with one embodiment of        the invention, the material of the layer 13′, 23′ on the inner        side of the surface layer is a material that conducts heat        particularly well and has an effective thermal conductivity        of >70 W/mK. The thermal conductivity and/or the other material        properties of the surface layer and the layer on the inner side        of the surface layer can also be similar, so that the surface        layer 14′, 24′ on the outer side and the layer 13′, 23′ on the        inner side of the surface layer—constituting layered wholes in        the sense of the manufacturing technique—may have the same        material properties, so that in accordance with one embodiment        the thermal conductivity of the material layers of the thermo        roll shell is in a range of 20-70 W/mK.    -   As shown in FIG. 15, the heat transfer means include a material        layer 13′ which is arranged to form the innermost layer of the        thermo roll 101′ and which in accordance with one embodiment of        the invention is of a material whose thermal conductivity is        higher than the thermal conductivity of the surface layer 14′ in        contact with the fibrous web and surrounding the heat transfer        layer 13′. The material of this material layer serving as the        heat transfer layer 13′ can be a material that conducts heat        particularly well and has an effective thermal conductivity        of >70 W/mK.    -   As shown in FIG. 16, the heat transfer means include a material        layer 13′ of the thermo roll 101′, which material layer is        thermally more conductive and forms a heat transfer layer 13′        whose material in accordance with one embodiment of the        invention is a material that conducts heat particularly well and        has an effective thermal conductivity of >70 W/mK, which        material layer is outside the innermost layer 11′ that is        thermally less conductive. The material of the innermost layer        11′ has been selected optimally with respect to internal        induction heating.        In accordance with one embodiment of the invention, the layer        13′, 23′ that conducts heat particularly well can be        manufactured, for example, of copper or a copper alloy, such as,        for example, CuCrZr. As the material of the heat transfer layer        13′, 23′ it is also possible to use brass, tin, aluminum, zinc,        chrome, zirconium, nickel, steel or the like. The material of        the heat transfer layer can also be an alloy or a composition        metal containing above-mentioned metals. The material of the        heat transfer layer can thus be a conventional material, such as        steel.

Said heat transfer means also include flow passages in which a heattransfer medium, such as oil, water, steam, air or another similarflowing gaseous or liquid heat transfer medium is flowing. The heattransfer means arranged in accordance with the invention serve toenhance heat transfer from the flowing medium to the outer surface 14a′, 24 a′ of the thermo roll in the case of heating of the thermo rolland, correspondingly, they serve to enhance heat transfer from thethermo roll to the flowing medium in the case of cooling of the thermoroll. Heat is transferred to the thermo roll and/or from the thermo rollusing the heat transfer medium through flow passages 15′, 25′, 151′,152′ situated inside the shell or through a center passage 30′ of thethermo roll or, alternatively, advantageously through both the centerpassage 30′ of the thermo roll and the flow passages 15′, 25′, 151′,152′ situated inside the shell.

In particular in connection with the heating and cooling stages of thethermo roll, for example, when there is a transition from the runningstate to the servicing state or vice versa, it is advantageous toheat/cool the thermo roll through the shell passages and the centerpassage in order that the thermal stresses in the thermo roll shall notbecome too great. When the thermo roll is heated/cooled only through theshell passages, which are situated in the material layer having goodthermal conductivity or in its immediate vicinity, the thermal stressesof the thermo roll may rise to too high a level as the change intemperature is directed to a substantial extent to said material layer,which functions as a heat transfer layer. During the heating or coolingof the thermo roll it is advantageous to use a separate heat transferpassage system in a thermally less conductive material layer situated onthe inner side or on the outer side of the material layer that functionsas the heat transfer layer to even out the temperature difference insidethe thermo roll such that the thermal stresses remain in a range thatcauses no fatigue in the structure. Heat can also be produced for theinterior parts of the thermo roll in other ways, for example, byinternal induction heating, so that cooling can be accomplished, asmentioned above, by means of the heat transfer medium flowing in theflow passages. It is also possible to heat the thermo roll 10′, 20′,101′ by hot air blowing.

The shell structure of the thermo roll 10′, 20′, 101′ in accordance withthe invention is such that the properties of the material, in particularthermal conductivity and mechanical strength, are designed to change ina layer by layer fashion in the radial direction of the thermo roll 10′,20′, 101′ to improve the operating characteristics of the thermo roll.Since it is generally not possible to achieve the optimum with respectto thermal conductivity and mechanical strength simultaneously with thesame material, in accordance with the arrangement of the invention amaterial having the best property in view of the whole is selected foreach area in the radial periphery of the thermo roll 10′, 20′, 101′.

FIG. 10 illustrates typical different material layers of the shell ofthe thermo roll in accordance with one embodiment of the invention andthe location of flow passages or how it is possible to place them in theshell of the thermo roll. Instead of the three layers shown, the thermoroll in accordance with the invention may also comprise more layers, forexample, four layers, or two layers as shown in FIG. 15. Depending onthe embodiment of the invention, a given material layer can have thefunction of a mainly load-bearing layer or the function of a mainlyheat-transferring layer or a given material layer can have the functionsof both a load-bearing layer and a heat-transferring layer.

In the example of FIG. 10, the inner layer 11′ functioning as the baselayer of the thermo roll is formed of a load-bearing material layer 11′.The function of the material layer arranged around the inner layer 11′and forming a heat transfer layer 13′ is to transfer efficiently theheat capacity introduced by means of the heat transfer medium flowinginto the thermo roll to the surface layer 14′ of the thermo roll and tothe outer surface 14 a′ of the thermo roll shell. There can be flowpassages at several different levels and the thermo roll may have flowpassages situated in different layers inside the shell, such as the flowpassages 15′, 151′, 152′ and the center passage 30′ inside the thermoroll shell.

In the left-hand portion of the cross section of principle of the thermoroll shown in FIG. 10, there are two adjacent flow passages 15′ in thearea of the boundary surface where the inner layer 11′ and the heattransfer layer 13′ of the shell of the thermo roll join each other, i.e.in the area of their boundary zone, which flow passages extend partly tothe heat transfer layer 13′ and partly to the inner layer 11′. In thatcase, the flow passage is formed by recesses or grooves 12′ situated inopposed relationship in the outer surface of the inner layer and in theinner surface of the outer layer.

The thermo roll may also be provided with flow passages 151′ like theones shown in the right-hand portion of the cross section of FIG. 10 andsubstantially placed in the heat transfer layer, which flow passages arein this example entirely inside the heat transfer layer 13′ or the layer13′ on the inner side of the surface layer, entirely surrounded by theheat transfer material.

The thermo roll may also be provided with flow passages that are insideor outside a thermally highly conductive material layer or the heattransfer layer. In the example of FIG. 10, a flow passage 152′ is in itsentirety in the inner layer 11′ surrounded by the heat transfer layer13′, inside the heat transfer layer 13′, the flow passage 152′ beingformed, for example, by a bore made in the inner layer 11′. The flowpassage can also be equally well in its entirety in the surface layersurrounding the heat transfer layer, outside the heat transfer layer,the flow passage being formed, for example, by a bore made in thesurface layer.

More generally, FIG. 14B shows, by means of four flow passages 15′, flowpassage shapes formed in the boundary surface of two mating parts thatform the thermo roll 10′. As shown in FIG. 14B, the flow passage 15′ canbe formed in its entirety by a recess or a groove 12 i made in the outersurface of the inner layer I, the depth of which recess or groove 12 ifrom the outer surface of the layer I in the radial direction of thethermo roll can be selected to be suitable, for example, when arrangingthe heat transfer area of the flow passage to be as desired or whenarranging the flow velocity of the heat transfer medium to be asdesired, or the flow passage 15′ can be formed in its entirety by arecess or a groove 12 o made in the inner surface of the outer layer O,the depth of which recess of groove 12 o from the inner surface of thelayer O can be selected to be suitable, or the flow passage 15′ can beformed of partly or totally coincident flow grooves 12 i, 12 o situatedboth in the inner layer I and in the outer layer O.

The flow passages can be provided, in accordance with the example ofFIG. 10, with flow tubes 16′ either by providing the flow passages withtubes afterwards or by placing flow tubes 16′ inside the heat transferlayer 13′, inside another layer of the shell or inside a flow passage15′, 151′, 152′ formed in the boundary zone of two layers in connectionwith manufacture, e.g. hot pressing. Thus, the flow passages 15′ placedin the shell of the thermo roll radially at a selectable distance fromthe outer surface of the thermo roll can be provided with tubes, as theflow passages 152′. The placement of the flow passages 15′, 151′, 152′can be accomplished in accordance with the invention in different waysas described hereafter. The measurements of the material layers and themeasurements and the placement density of the flow passages aredetermined, among other things, by the material arrangement to be chosenand by the heat capacity to be transferred in each site of use.

FIGS. 11-13 are a figure series of a first advantageous embodiment ofthe invention, in which the thermo roll 10′ is formed of three layerswhich are placed one upon the other and which are or may be of differentmaterials. The structure of the shell of the thermo roll 10′ is suchthat the properties of the material, in particular thermal conductivityand mechanical strength, are designed to change in a layer by layerfashion in the radial direction of the thermo roll 10′ to improve theoperating characteristics of the thermo roll. Since it is generally notpossible to achieve the optimum with respect to thermal conductivity andmechanical strength simultaneously with the same material, in accordancewith the arrangement of the invention a material having the bestproperty in view of the whole is selected for each layer of themulti-layer thermo roll 10′.

As shown in FIG. 11, the inner layer 11′ functioning as the base layerof the thermo roll 10′ is thus formed of a solid load-bearing materiallayer 11′, which is in this example a relatively stiff, advantageouslytubular part 11′. The inner surface 11 b′ of the inner layer 11′ definesinside itself a center passage 30′ of the thermo roll 10′. In thisexample, the inner layer 11′ carries most of the thermo roll's 10′ ownweight, of nip forces, and of the loads caused by other external forces.This cylindrical inner layer 11′ is of a strong, tough material thatwithstands bending well, but it need not necessarily be good in respectof its thermal conductivity, on the contrary, among other things, whenheating and/or cooling merely through the flow passages provided in theshell of the thermo roll, thermal insulation capacity may be anadvantage to limit heat appropriately for the treatment process of thefibrous web and to prevent heat transfer to bearing arrangements (notshown) of the thermo roll and therethrough to the frame structures ofthe machine.

FIG. 11 shows an inner layer 11′ of the thermo roll 10′, the outersurface 11 a′ of which inner layer is provided with recesses or grooves12′ which are at positions designed to be advantageous for flow passagesand which, as being in the harder material 11′, can serve as forms thatguide drilling when flow passages 15′ are formed later. The grooves 12′are placed and dimensioned in an optimal manner, in particular to assurean even transfer and distribution of heat. The grooves 12′ are made inthe inner layer 11′ forming the base of the thermo roll, for example, bymachining, for example, by milling or drilling, or by forging orpressing, such as hot pressing, or by etching. It may be emphasized thatin the layer on the inner side of the surface layer/in the heat transferlayer and in the inner layer of the shell of the thermo roll 10′ shownin FIGS. 11-13 there can also be flow passages (not shown), for example,a flow passage can be in its entirety in the inner layer 11′ surroundedby the heat transfer layer 13′, so that the flow passage is formed, forexample, by a bore made into the inner layer 11′, or the flow passagecan also be equally well in its entirety in the heat transfer layer 13′surrounding the inner layer 11′.

FIG. 12 is a partial cross-sectional view of a semi-finished product ofthe thermo roll, in which a material layer is arranged around thegrooved inner layer 11′ of the shell 10′ shown in FIG. 11, whichmaterial layer forms the heat transfer layer 13′ having an outer surface13 a′. The inner surface 13 b′ of the material/the material layer 13′forming the heat transfer layer 13′ or the main part of the heattransfer layer 13′ and having in this exemplifying embodiment the bestthermal conductivity of the thermo roll 10′ conforms to the shapes ofthe outer surface 11 a′ and to the grooves 12′ of the inner layer 11′ inFIG. 12. An enlarged detail of the area BB in FIG. 12 is shown on theright side of FIG. 12, in which in the groove 12′ placed in the outersurface of the inner layer 11′ there is material that is advantageouslysofter than the material of the inner layer 11′, such as the material ofthe heat transfer layer 13′. The grooves 12′ of the semi-finishedproduct are opened, for example, by drilling, using the groove 12′ ofthe harder material as a guide groove. The finished bore of the rollconstruction is thus, for example, like the partial section AA showing adetail that has been drilled open on the left side of FIG. 12.

Alternatively, the heat transfer layer 13′ can be, for example, as shownin FIG. 14B, cylindrical in shape, in which case it would not extend tothe area of the grooves 12′ in one possible intermediate stage ofmanufacture shown in FIG. 12. Generally, in the inner surface 14 b′ ofthe surface layer 14′ and/or in the inner surface of some layer on theinner side of the surface layer 14′ there can be recesses or grooves12′, whose cross-sectional profile shape constitutes a portion of thecross-sectional profile of the flow passage 15′, so that the recess orthe groove 12′ forms the flow passage 15′ together with the outersurface of the inner material layer. In the outer surface of somematerial layer situated on the inner side of the surface layer 14′ therecan also be recesses or grooves 12′, whose cross-sectional profile shapeconstitutes a portion of the cross-sectional profile of the flow passage15′, so that the recess or the groove 12′ forms the flow passage 15′together with the inner surface of the outer material layer. Moregenerally, the inner surface and/or the outer surface of the materiallayer of the thermo roll shell can be provided with recesses or grooves12′ to form flow passages 15′ or to receive flow tubes 16′.

FIG. 13 is a partial cross-sectional view of the shell of the thermoroll 10′ in accordance with a first embodiment of the invention, whichshell is optimized in respect of its heat transfer properties andprovided with flow passages 15′. The layer on the inner side of thesurface layer/the heat transfer layer 13′ is surrounded by awear-resistant surface layer 14′, the layer thickness of which isappropriately thinner than that of the layer on the inner side of thesurface layer/the heat transfer layer, and the properties and thesurface quality of the outer surface 14 a′ of which meet the wear,process and other requirements set by use. The flow passages 15′situated in the shell of the thermo roll 10′ for a flowing heat transfermedium, which flow passages are in this case heat transfer bores 15′that are mainly parallel or almost parallel to the axis of the thermoroll 10′, are formed in the area of the grooves 12′ situated on thesurface of the inner layer 11′ and illustrated in FIG. 11, which grooves12′ are filled, as shown in FIG. 12, temporarily for the time ofmanufacture with a soft material, which is easy to drill open in theaxial direction in a semi-finished product or in a full-size thermoroll. In this embodiment of the invention, the grooves 12′ serve asforms which are placed in the harder material 11′ and which guidedrilling when the flow passages 15′ are drilled open. Generally, theflow passage 15′ can open in the boundary zone of two material layersinto the inner surface or the outer surface of the material layer, i.e.here the flow passage 15′ opens in the boundary zone of the heattransfer layer 13′ and the inner layer 111′ to the outer surface 11 a′of the inner layer 11′ and to the inner surface 13 b′ of the heattransfer layer 13′. The function of the heat transfer layer 13′ is toefficiently transfer the heat capacity introduced into the thermo roll10 to the outer surface 14 a′ of the surface layer 14′ of the thermoroll. The material having the best thermal conductivity is placed mainlybetween the system of flow passages 15′ designed to be placed at thegrooves 12′ and the surface 14 a′, in an area as large as possible inthe heat transfer layer 13′. By this means, efficiency is achieved inheat transfer, whereby the temperature between the flowing medium,advantageously oil, and the surface 14 a′ becomes small.

FIG. 13 shows that the thermo roll has a surface layer 14′ on the layersituated on the inner side of the surface layer/on the heat transferlayer 13′, by means of which layer the thermo roll becomes a three-layerthermo roll. It shall be emphasized that the existence of the surfacelayer 14′ is only optional and that the existence of the surface layeris substantially more important from the viewpoint of the wearresistance of the thermo roll and its surface structure withstandingcompression and deflection loads. An advantageous surface layer isformed, for example, of a steel layer whose thickness can advantageouslybe 1-5 mm. The surface layer can also be a thin hardcoating of 0.01-2mm.

FIG. 14B illustrates ways of forming the flow passage 15′ between twolayers of the shell of the thermo roll 10′, which layers are placed oneupon the other and which layers function as mating parts, in the area ofthe boundary surface of the mating parts. The grooves 12 i and 12 o canbe provided beforehand on the boundary surfaces of the mating parts,i.e. the layers of the shell, such that when the mating parts areassembled, the grooves form a flow passage 15′. The flow passage 15′ canthus be formed only of the groove 12 i provided in the inner part oronly of the groove 12 o provided in the outer part or of groovesprovided both in the inner and in the outer part. The grooves 12 i, 12 osituated both in the inner and in the outer part and forming the flowpassage 15′ can be advantageously placed exactly in opposed relationshipor the grooves 12 i, 12 o can be laterally partly displaced with respectto each other.

FIG. 14A illustrates a thermo roll 20′ assembled of at least two partsin accordance with a second advantageous embodiment of the invention.Here, the shell of the thermo roll 20′, in particular the material layerthat forms a heat transfer layer 23′ of the thermo roll shell or themain part of said heat transfer layer, is formed of parts 231′, 232′,233′, etc. placed/assembled one after the other, and a surface layer 24′of the thermo roll is formed of at least one part, said part beingdisc-shaped, annular or cylindrical. The part forming the surface layerand/or the part forming the heat transfer layer can thus be a continuouscylinder extending over the entire length of the thermo roll 20′ andbeing coaxial therewith. The surface layer 24′ of the thermo roll 20′can also be composed of at least two surface layers of cylindrical parts(i.e. surface layers of sectional rolls which are shorter with respectto the length of the thermo roll) placed/assembled one inside the otherand/or one after the other in the axial direction, which cylindricalparts are formed of parts that are continuous in the circumferentialdirection.

In the thermo roll in accordance with one embodiment of the invention,at least one part, such as the shell and/or the end part, has anon-homogeneous thermal conductivity or thermal expansion coefficient,i.e. thermal conductivity or thermal expansion coefficient changing withrespect to location. Thus, the thermal conductivity of the shell inparticular changes in the radial direction and/or the thermalconductivity of the end part in particular changes as a function of theaxial direction. Said property can be provided by powder metallurgicalmeans.

The part forming the layer on the inner side of the surface layer/theheat transfer layer 23′ is disposed or the parts forming the heattransfer layer 23′ are assembled in the axial direction around an innerpart, i.e. an inner layer 21′ which functions as the base of the thermoroll 20′ and is formed of one or more continuous tubular parts. For thesake of clarity, FIG. 14A does not show the surface layer 24′ of thethermo roll 20′ assembled around the heat transfer layer 23′. Thesurface layer 24′ can be formed of one or more parts or it can be made,instead of a continuous part/an assembly of continuous parts, into acontinuous material layer arranged around the material layer on theinner side of it, for example, by casting, welding, thermal spraying,layering, pressing or by another equivalent manufacturing method forminga continuous layer. It shall also be noted that the thermo roll 20′ inaccordance with the invention can also be without the surface layer 24′and/or without the inner layer 21′.

In a second embodiment of the invention, flow passages 25′ or flowopenings 25′ can be provided in the separate parts 231′, 232′, 233′,etc. already before the assembly of the thermo roll 20′, as shown in themiddle part of FIG. 14A, such that, when the parts 21′, 231′, 232′,233′, etc. have been joined together, the flow passages 25′ areconnected and form a system of flow passages 25′ going through in theassembled thermo roll. The separate parts 21′, 231′, 232′, 233′, etc.and 24′ can be advantageously provided already before the assembly ofthe thermo roll 20′ with the possibly needed forms (not shown) requiredby the fixing and/or joint members such that, when the shell parts havebeen joined together, the fixing and/or joint forms, for example, theholes of fixing bolts or joint forms with interlocking shapes, fit oneanother. The mating surfaces of the parts are machined before assemblyor they are already sufficiently smooth so that the assembled thermoroll 20′ is tight.

The parts forming each material layer 21′, 23′ and 24′ in FIG. 14A areformed in respect of inside and outside measurements and surface qualitysuch that they can be assembled appropriately in connection with eachparticular attachment technique. Thus, the joint between the outersurface 21 a′ of the inner layer and the inner surface 23 b′ of thelayer on the inner side of the surface layer/the heat transfer layer aswell as the joint between the outer surface 23 a′ of the heat transferlayer and the inner surface 24 b′ of the surface layer each have suchmechanical fit values and the above-mentioned surfaces each have suchsurface quality values as are determined according to the materialproperties of each part to be attached and according to the desiredmethod of attachment.

In the thermo roll 20′ in accordance with a variant of the secondembodiment of the invention (not shown by a figure), the flow passagesarranged in the shell of the thermo roll are arranged in connection withthe layer situated on the inner side of the surface layer/the heattransfer layer 23′ in the boundary zone of the heat transfer layer 23′and the inner layer 21′. In that case, the flow passages are formed byflow passage recesses or grooves which are formed in the outer surface21 a′ of the tubular inner part 21′ and which are inner recesses orgrooves in the radial direction of the thermo roll and by curvedperipheral portions provided in the cylindrical inner surface 23 b′ ofthe part/parts forming the heat transfer layer 23′ and located inopposed relationship to each recess or groove. The inner surfaces 23 b′may also comprise outer recesses or grooves in the radial direction ofthe thermo roll, which recesses or grooves form the outer part of theflow passages. When the inner part 21′ and the part/parts forming theheat transfer layer 23′ have been assembled, the inner and outer partsof the flow passages form together a system of through-going flowpassages.

FIG. 15 shows the shell of a thermo roll 101′ in accordance with a thirdembodiment of the invention. The shell of the thermo roll 101′ of FIG.15 comprises two material layers whose thermal conductivity changes in alayer by layer fashion in the radial direction of the thermo roll 101′.A material layer that conducts heat better is arranged to form one heattransfer means of the thermo roll 101′, said material layer forming aheat transfer layer 13′, which in FIG. 15 is on the inner side of athermally less conductive surface layer 14′.

The thermo roll 101′ shown in FIG. 15 can be heatable from inside, sothat the inner surface 13 b′ of the inner heat transfer layer 13′defines within itself a center passage 30′ as a second heat transfermeans of the thermo roll 101′, a heat transfer medium flowing in saidcenter passage, or the center passage 30′ is provided with a third heattransfer means, such as an internal induction heating coil in a Tokudenroll, or the thermo roll 101′ can also be provided with flow passages(not shown) arranged in the shell by means of fourth heat transfermeans, among other things, to reduce thermal stresses during heating andcooling of the shell of the thermo roll 101′. One big problem withinternally heatable rolls has been the relatively high heat transferresistance caused by a thick shell, for example, when the shell materialhas had low thermal conductivity and/or the heat transfer distance tothe outer surface has been large, wherefore the temperature differencebetween the inner parts and the outer surface of the thermo roll hasbeen great, readily of the order of 100° C. If the material layer thatforms a heat transfer area, i.e. an area across which the heat capacityto be transferred to the fibrous web is transferred to the shell of thethermo roll and across which the heat capacity to be transferred fromthe fibrous web is transferred from the shell of the thermo roll, forexample, a layer between the flow passages arranged in the shell of thethermo roll 101′ and its outer surface, in the case of FIG. 15 the layerbetween the center passage 30′ and the outer surface 14 a′, mainly theheat transfer layer 13′, is mostly, for example, of copper or anotherequivalent material that conducts heat particularly well, heat transfercan be enhanced considerably. In practice, the temperature differenceeffective across the shell is reduced to a fraction with the same totalcapacity, for example, from 100° C. to about 20-25° C.

In FIG. 15, the heat transfer layer 13′ constituting the main part ofthe shell of the thermo roll 101′ can be of a material that conductsheat particularly well, for example, of a copper alloy. In addition tothis, as the surface layer 14′ it is possible to use a material layer,such as a steel layer, that provides strength against compression anddeflection loads. In the case of FIG. 15, a particularly goodarrangement is to place the heat transfer layer 13′ in the inner partsof the thermo roll 101′ and the thinner steel shell 14′ outside it,although a different arrangement is also feasible. As suitably alloyed,the material used for the heat transfer layer 13′, such as copper or anequivalent material conducting heat better than steel, can besufficiently strong to form the base or the load-bearing layer of thethermo roll, even so that only a thin hardcoating is needed to form thesurface layer 14′, i.e. for the outer surface 14 a′ of the thermo roll101′. The innermost layer of the thermo roll 101′ serving as the heattransfer layer 13′ can be the layer mainly carrying the load caused bythe thermo roll's own weight, nip forces and other external forces orthe layer 13′ conducting heat better than the surface layer 14′ can bearranged to form the load-bearing layer.

FIG. 16 shows the shell of the thermo roll 101′ in accordance with avariant of the third embodiment of the invention. The shell of thethermo roll 101′ in FIG. 16 comprises two material layers whose thermalconductivity changes in a layer by layer fashion in the radial directionof the thermo roll 101′. A material layer that conducts heat better isarranged to form one heat transfer means of the thermo roll 101′, saidmaterial layer forming a heat transfer layer 13′ which in FIG. 16 isoutside the thermally less conductive innermost layer 11′. The materialof the innermost layer 11′ is selected optimally with respect tointernal induction heating such that eddy currents are induced well inthe material. Outside the heat transfer layer 13′ there can also be athin, thermally less conductive surface layer 14′, said surface layerbeing shown with broken lines in FIG. 16. The thermo roll 101′ shown inFIG. 16 can be heatable from inside, so that the inner surface 11 b′ ofthe innermost layer 11′ defines within itself a center passage 30′ as asecond heat transfer means of the thermo roll 101′, a heat transfermedium flowing in said center passage, or the central passage 30′ isprovided with a third heat transfer means, such as an internal inductionheating coil in a Tokuden roll, or the thermo roll 101′ can also beprovided with flow passages (not shown) arranged in the shell by meansof fourth heat transfer means, among other things, to reduce thermalstresses during heating and cooling of the shell of the thermo roll101′.

In FIG. 18, the heat transfer layer 13′ constituting the main part ofthe shell of the thermo roll 101′ can be of a material that conductsheat particularly well, for example, of a copper alloy. In addition tothis, as the possible surface layer 14′, it is possible to use amaterial layer, such as a steel layer, that provides strength againstcompression and deflection loads. In the case of FIG. 16, a particularlygood arrangement is to arrange the thick heat transfer layer 13′ to formthe surface layer of the thermo roll 101′ outside the innermost layer11′ whose material is, for example, iron, steel, aluminum or anothersimilar material well heatable by induction. As suitably alloyed, thematerial used for the heat transfer layer 13′, such as copper or anequivalent material conducting heat better than steel, can besufficiently strong to form the base or the load-bearing layer of thethermo roll, even so that only a thin hardcoating is possibly needed toform the surface layer 14′, i.e. for the outer surface 14 a′ of thethermo roll 101′. The heat transfer layer 13′ can be the layer mainlycarrying the load caused by the thermo roll's own weight, nip forces andother external forces or the innermost layer 11′ optimal with respect toinduction heating can be the load-bearing layer.

By placing a steel shell outermost, i.e. to form the surface layer 14′,more deflection and compression stiffness is imparted to the thermoroll, because the strong steel layer is situated farther from theneutral axis of deflection. Thus, the surface layer 14′ of the thermoroll 101′ can also serve as the layer mainly carrying the load caused bythe thermo roll's own weight, nip forces and other external forces orthe layer 14′ that is thermally less conductive than the inner heattransfer layer 13′ can be arranged to form mainly the load-bearinglayer.

In FIG. 16, from the thermal viewpoint, the placement of the steel shell14′ outermost is advantageous in the sense that, as a poorer heatconductor, the steel layer 14′ sort of slows down heat transfer in thevicinity of the outer surface 14 a′, so that temperature differenceshave time to even out in the material layer that transfers heat betterand forms the heat transfer layer 13′, such as a copper layer. Theevening out of the temperature differences is particularly important inthe Tokuden construction in which it is necessary to use special heatequalization chambers in the shell of the thermo roll because of theuneven heating effect of the heating elements arranged in sections,which heat equalization chambers are partly filled, for example, with asuitable filling agent, such as naphthalene.

The arrangement shown in FIGS. 15 and 16 makes it possible to combinethe internal heating of the thermo roll 101′, such as Tokuden heating,and a layered thermo roll shell made of at least two material layersand/or flow passages shown in FIGS. 10-14B and placed in the shell ofthe thermo roll can be arranged in the thermo roll 101′ for coolingand/or for heating.

The advantages of the embodiments shown in FIGS. 15 and 16 includesignificantly better thermal conductivity in the shell of the thermoroll 101′, which leads to the following benefits: a higher totalcapacity is possible; a higher surface temperature is possible; a lowerinternal temperature is needed for the same surface temperature, whichmeans that the heat introduction means and machine members arranged inthe interior of the thermo roll 101′ last longer; and a higher specificheating capacity, so that a smaller roll diameter is possible.

When selecting the combination of materials of the different layers inFIGS. 10-16, strength and thermal expansions have been taken intoaccount as limitations.

In FIGS. 10-14, the material used for the inner layer 11′, 21′ is, forexample, carbon steel or cast iron, the benefits of which can beconsidered to be strength, inexpensive application and mechanicalreliability. The inner layer 11′, 21′ can be, for example, a forgedsteel shell. The layer on the inner side of the surface layer/the heattransfer layer 13′, 23′ is formed, for example, of copper oradvantageously of a copper alloy, such as, for example, CuCrZr. As thematerial of the layer on the inner side of the surface layer/the heattransfer layer 13′, 23′ it is also possible to use brass, tin, aluminum,zinc, chrome, zirconium, nickel, steel or the like. An alloy or acomposition metal containing said metals can also be the material of theheat transfer layer.

The material used for the surface layer 14′, 24′ is, for example, lowcarbon steel. Alternatively, the surface is provided with a hardwear-resistant layer by means of a hardcoating, for example, a chromecoating or a ceramic coating or by thermally spraying or welding ahardlayer to the surface. Alternative other properties the surface layeris desired to have are strength, toughness, hardness, wear resistance,suitable thermal expansion, surface quality, cleanability or the like.If the surface layer 14′, 24′ is a poorer heat conductor than the heattransfer layer 13′, 23′, the surface layer is sought to be kept thinnerthan the heat transfer layer in order that the total thermalconductivity of the thermo roll shell shall not be reduced too much. Thesurface layer 14′, 24′ can be even very thin and, for instance, a chromeplated layer or another hardcoating or ceramic layer can be applied ifthe mechanical properties of the layer on the inner side of the surfacelayer/the heat transfer layer 13′, 23′ are sufficient to withstand thestresses arising through nip load and the thermal stresses of the thermoroll in order that the possibly hard and brittle surface layer shallremain fixed to the heat transfer layer 13′, 23′.

It is possible to transfer the high heating and cooling capacitiesrequired by the new calendering methods mentioned at the beginning, thusensuring that sufficient heat capacity is transferred through the shellof the thermo roll 10′, 20′ to the nip and further to the fibrous web tobe treated, and vice versa, also by reducing the heat transfer distancebetween the heat transfer area of the thermo roll 10′, 20′ and the outersurface 14 a′, 24 a′ of the surface layer 14′, 24′ of the shell.

In the thermo roll in accordance with one advantageous embodiment of theinvention, a significant improvement in heat transfer is achieved byarranging a heat transfer area close to the surface layer of the thermoroll 10′, 20′, in which connection the heat transfer area of the thermoroll can be heated and/or cooled by means of flow passages 15′, 25′,151′, 152′ arranged in the shell of the thermo roll 10′, 20′. It is thenalso possible to use less unconventional materials or conventionalmaterials, such as ferrous metals, advantageously steel, for the heattransfer layer 13′, 23′ and/or for the surface layer 24′, 14′. In orderthat heat may be transferred close to the surface 14 a′, 24 a′, at leastsome of the flow passages 15′, 25′, 151′, 152′ are placed close to thesurface 14 a′, 24 a′, as measured at their center line, advantageouslyat a distance of 50 mm at the most from the outer surface 14 a′, 24 a′of the thermo roll, preferably at least some of the flow passages 15′,25′, 151′, 152′ are placed, as measured at their center line, at adistance of 10-40 mm from the outer surface 14 a′, 24 a′ of the thermoroll. When the flow passages are placed so close to the surface 14 a′,24 a′, the thermo roll 10′, 20′ can be, in a layer by layer fashion,entirely or partly of steel, cast iron or another suitable material.

When the heat transfer area is arranged close to the surface layer ofthe thermo roll 10′, 20′, 101′ the structure of the thermo roll can besuch that the inner part of the thermo roll is formed of a continuous,advantageously tubular part, which forms the innermost material layer11′, 21′ of the thermo roll or the heat transfer layer 13′, 23′ placedon the innermost material layer. To form flow passages 15′, grooves 12′,12 b′ are formed, for example, by milling or hot pressing in the outersurface 11 a′, 21 a′ of the innermost material layer 11′, 21′ and/or inthe outer surface 13 a′, 23 a′ of the layer on the inner side of thesurface layer/the heat transfer layer 13′, 23′, the cross-sectionalprofile shapes of which grooves constitute a portion of thecross-sectional profiles of the flow passages 15′, 25′ of the heattransfer medium. The flow passages 15′, 25′ can also be in theirentirety in accordance with the invention passages that are formed, forexample, by drilling into a material that conducts heat particularlywell.

The flow passages 15′ are thus formed between the outer material layer,which can be the heat transfer layer 13′, 23′ or the surface layer 14′,24′ of the thermo roll, and the inner material layer, which iscorrespondingly the material layer 11′, 21′ or the heat transfer layer13′, 23′.

The surface layer 14′ of the base of the single- or multi-layer thermoroll can be formed, for instance, using the HIP, welding, soldering orthermal contraction method.

The surface layer 14′ of the shell of the single- or multilayer thermoroll or, generally, some layer of the shell of the thermo roll can beformed in a separate manufacturing stage using the HIP method, bywelding, casting, forging or milling. The surface layer 14′ or,generally, some layer of the shell of the thermo roll can be fixed orassembled onto the layer situated on the inner side in a separatemanufacturing stage using the HIP method, by welding, soldering orthermal contraction, using an interlocking joint or by means of bolts.

In order that the temperature distribution of the surface 14 a′, 24 a′of the thermo roll 10′, 20′ might be made even, it is advantageous toform, for the purpose of providing flow passages 15′ for a heat transfermedium,

-   -   a large number of bores in the layer 13′, 23′ which is on the        inner side of the surface layer 14′, 24′ and which is most        advantageously of a metal material that conducts heat        particularly well, and/or    -   a large number of grooves 12′ in the inner surface 13 a′, 23 a′        of the layer 13′, 23′ on the inner side of the surface layer        14′, 24′.

When the layers of the thermo roll 10′, 20′ are of the same material ina layer by layer fashion, an advantage arising from the arrangementdescribed above is that problematic thermal stresses are not created inthe shell of the thermo roll, especially not in the boundary zone of thematerial layers. In addition, the load-bearing capacity of the thermoroll 10′, 20′ is good when, for example, steel is used as the materialof the material layers.

FIG. 17 shows an exemplifying diagram of the temperature distribution inthe shell of the thermo roll in accordance with one first embodiment ofthe invention. The computational temperature distribution of thematerial layers, i.e. the inner layer 11′, the heat transfer layer 13′and the surface layer 14′, of the thermo roll like the one shown inFIGS. 11-13 and optimized in respect of its heat transfer properties isshown by means of a graph of temperature [° C.] against radius [m]. Themeasurements of the different layers of the shell of this oil-heatablethermo roll are, expressed as layer thicknesses in the radial directionof the thermo roll, as follows: the thickness of the inner layer 11′ is35 mm, the thickness of the heat transfer layer 13′ is 60 mm and thethickness of the surface layer 14′ is 5 mm, while the outside diameteris 1200 mm. When the radius of the inner layer 11′ of the example rollis between 0.500 m and 0.535 m, temperature is calculated to remainconstant 222.5° C., which is also the temperature of heating oil. Theflow passages are computationally at a radius of 0.535 m in the boundaryzone of the inner layer 11′ and the heat transfer layer 13′. Thetemperature of the heat transfer layer 13′ in a radial range of 0.535 mto 0.595 m decreases almost linearly from the value of 222.5° C. to thevalue of 210° C. The temperature of the steel surface layer 14′ in aradial range of 0.595 m to 0.600 m decreases linearly sharply from thetemperature value of 210° C. to the value of 200° C., the totaltemperature difference between the heating oil and the surface 14 a′being thus 22.5° C. in the example of the diagram.

In the thermo roll 10′, 20′, 101′ in accordance with one embodiment ofthe invention as well as in a semi-finished product for the thermo roll10′, 20′, 101′ in accordance with one embodiment of the invention, theinner surface 13 b′, 14 b′, 23 b′, 24 b′ and/or the outer surface 11 a′,13 a′, 21 a′, 23 a′ of the material layer is/are provided with recessesor grooves 12′, whose cross-sectional profile shapes constitute aportion of the cross-sectional profile of the flow passages 15′, 25′, sothat the recesses or grooves 12′ form flow passages 15′, 25′ togetherwith the inner surface of the outer material layer or with the outersurface of the inner material layer to form the flow passages 15′, 25′or to receive flow tubes 16′.

In the method of manufacturing a thermo roll in accordance with theinvention, material layers are arranged one inside the other in theshell of the thermo roll 10′, 20′, 101′ to enhance the heat transferproperties of the thermo roll 10′, 20′, 101′. In the embodiments of theinvention shown in FIGS. 10-14A, a material layer having higher thermalconductivity than the thermal conductivity of the inner layer 11′, 21′can be arranged between the inner layer 11′, 21′ and the surface layer14′, 24′ of the thermo roll 10′, 20′ to form the heat transfer layer13′, 23′, and a material layer having higher thermal conductivity thanthe thermal conductivity of the surface layer 14′ can be arranged toform the heat transfer layer 13′ as the innermost material layer of thethermo roll 101′ shown in FIGS. 15 and 16.

In the methods for manufacturing the thermo roll 10′, 20′, 101′ intendedfor the treatment of a fibrous web, the shell of which thermo rollcomprises at least two material layers, which thermo roll or the shellof which thermo roll is provided with heat transfer means for heatingand/or cooling the shell of the thermo roll, advantageously by means ofa heat transfer medium, in accordance with the first method of theinvention, at least two material layers 11′, 13′, 14′, 21′, 23′, 24′ arearranged radially one within the other in the shell of the thermo roll,which material layers are different in their manufacturing technique andwhich material layers are manufactured with respect to theirmanufacturing technique in different stages or by different methods, andheat transfer medium flow passages 15′, 25′, 151′, 152′ are arranged tobe confined by at least one of said material layers inside itself orsituated in a boundary zone of said material layers, and in accordancewith the second method of the invention, different material layers 11′,13′, 14′, 21′, 23′, 24′ are arranged in layers radially one within theother in the shell of the thermo roll, the thermal conductivities of atleast two of which material layers are different from one another, andthat heat transfer medium flow passages 15′, 25′, 30′, 151′, 152′ arearranged in at least one of said material layers or to be confined by atleast one of said material layers inside itself or to be situated in aboundary zone of said material layers.

A significant improvement of heat transfer can be achieved by arranginga heat transfer area close to the surface layer of the thermo roll 10′,20′.

Some advantageous exemplifying embodiments of the method ofmanufacturing the thermo roll 10′, 20′ are described in the following.At least one material layer, in particular the heat transfer layer 13′,of the material layers of the thermo roll shell of the thermo roll 10′in accordance with a first embodiment of the invention and of the thermoroll comprising a system of flow passages 151′ formed of tubes 16′ inaccordance with a variant of the first embodiment can be manufactured,in accordance with the invention, by pressing, advantageously by hotisostatic pressing, i.e. the HIP process, and by cutting associatedtherewith, when needed, and by the associated assembly, when needed. Thematerial layers of the thermo roll 10′ in accordance with the firstembodiment of the invention can also be manufactured by other methodsknown in themselves, for instance, the heat transfer layer 13′ can bemanufactured by casting it around the inner layer 11′.

The material layers, in particular the heat transfer layer 23′, of theshell of the thermo roll 20′ assembled of parts in accordance with asecond embodiment of the invention and of the thermo roll in accordancewith a variant of the second embodiment can be advantageouslymanufactured, in accordance with the invention, by hot pressing and bymilling associated therewith, when needed, and by the associatedassembly, when needed. The material layers of the thermo roll 20′ inaccordance with the second embodiment of the invention and, similarly,of the thermo roll in accordance with the variant of the secondembodiment can also be manufactured by methods known in themselves bymilling, casting or the like and, when needed, by the associatedassembly.

The manufacture of the shell of the thermo roll in accordance with thefirst embodiment of the invention by means of hot pressing is describedin the following. Tubular blank moulds dimensioned as desired for use inhot pressing are manufactured first and the HIP manufacturing techniqueis then used. The material used for the heat transfer layer 13′ as thestarting material of hot pressing is a fine metal powder, for example,CuCrZr, which is converted into a solid metal part in the process. Themetal powder is placed in the HIP mould, compacted by vibrating,encapsulated gas-tightly and pressed at high temperature and at highpressure for a certain time of action. The temperature, the pressure andthe time of action of the hot pressing process are controlled tooptimize the properties of the material that is hot pressed. In thiscase, typical hot pressing process parameters are represented by thefollowing exemplifying values: temperature 900±10° C., pressure 105±5MPa and time of action 2-3 h. If the inner layer 11′ of the thermo rollis included in the hot pressing process, for example, placed radially onthe inner side of the material which is initially in powder form andforms the heat transfer layer 13′, it receives advantageous stressrelief annealing due to the effect of temperature. In the process, thewaste of material is minimized and the part to be manufactured has agood surface quality and dimensional accuracy. Moreover, it becomespossible to manufacture complex shapes and to arrange optimally placedflow passages 15′ within the heat transfer layer.

In the hot pressing process, the drilling passages or grooves 12′ can befilled temporarily for the time of manufacture with a soft material,such as copper, which is easy to drill open in a semi-finished productor in a full-size thermo roll.

After completion of the hot pressing process and after cooling of theshell or a part of the shell of the thermo roll, it is machined, whenneeded, to produce the designed forms and the desired surface quality.

Thus, into the thermo roll 10′ in accordance with the first embodimentof the invention, in particular into the heat transfer layer 13′ of thethermo roll shell it is possible to drill flow passages 15′, i.e. heattransfer bores 15′, formed for a flowing heat transfer medium as shownin FIG. 13 by using the recesses or grooves 12′ in the surface of thebase layer 11′ as forms that guide drilling. In addition, when needed,the measurements and the surface quality of the part formed by hotpressing are arranged to be as desired for the subsequent attachment ofthe surface layer 14′, for example, by grinding. The surface layer 14′made, for example, of a solid material is attached to the thermo roll10′ around the heat transfer layer 13′, for example, by thermalcontraction, i.e. by joining with a shrink fit/an interference fit, bysoldering, welding, for example, by friction stud welding, or the like.Other applicable alternative coatings are described above in connectionwith the surface layer 14′. The grinding of the surface 14 a′ of thethermo roll 10′ to the desired surface quality is performed before thefirst time of process use, for example, after the final assembly of thethermo roll 10′.

In the thermo roll in accordance with a variant of the first embodimentof the invention, the flow passages 151′ in the heat transfer layer 13′of the shell are formed, for example, as follows. The metal powder thatis to form the heat transfer layer 13′ in hot pressing and the flowtubes 16 that are to form the flow passages 151′ are placed in a HIPmould. The metal powder is compacted by vibrating, encapsulatedgas-tightly and pressed at high temperature and at high pressure for acertain time of action, as in the case of the thermo roll in accordancewith the first embodiment. The flow tubes 16′ arranged in the heattransfer layer 13′ receive advantageous stress relief annealing in thehot pressing process due to the effect of temperature. In the hotpressing process, the waste of material is minimized and the partmanufactured has a good surface quality and dimensional accuracy.

In the thermo roll manufactured by hot pressing in accordance with avariant of the first embodiment of the invention, within the metalpowder that forms the heat transfer layer 13′, a system of flow passages151′, which is shown in FIG. 10 and placed in an optimal manner, can beformed out of tubes 16′ of steel or copper, as mentioned above. In thatconnection, different variants of flow passages, even ones previouslyimpossible to manufacture, such as, for example, passages 151′ whichdeviate from the axial direction of the thermo roll 10′, which passagesare spiral and at different distances in the radial direction from thecenter line of the thermo roll 10′, can be accomplished by placing theflow tube 16′ in the hot pressing process within the metal powderforming the heat transfer layer 13′ between the thermo roll base 11′forming the inner layer of the thermo roll 10′ and the surface layer 14′forming the outer surface. To optimize the distribution of heat, theflow tube 16′ can be dimensioned to be optimal in respect of its flowrate for each location where it is placed.

In the thermo roll assembled out of parts in accordance with anothervariant of the second embodiment of the invention, a system of flowpassages 151′ can also be formed, in the manner mentioned above, out oftubes 16′ made, for example, of steel or copper. In that connection,different variants of flow passages, even ones previously impossible tomanufacture, such as, for example, passages 151′ which deviate from theaxial direction of the thermo roll 20′, which passages are spiral and atdifferent distances in the radial direction from the center line of thethermo roll 20′, can be accomplished by placing the flow tube 16′ inconnection with the hot pressing process within the part/parts formingthe heat transfer layer 23′. To optimize the distribution of heat, theflow tube 16′ can be dimensioned to be optimal in respect of its flowrate for each location where it is placed.

The manufacture of the thermo roll 20′ in accordance with the secondembodiment of the invention is illustrated by means of FIG. 14A. Thethermo roll 20′ is assembled out of separate solid parts. The parts231′, 232′, 233′, etc. forming the material layers of the shell of thethermo roll 20′, in particular the parts forming the heat transfer layer23′ and the surface layer 24′ of the thermo roll, can be disc-shaped orannular or in particular cylindrical, as in FIG. 14A. They can becontinuous co-axial cylinders placed radially one within the other andextending over the entire length of the thermo roll 20′ or they can becontinuous in the circumferential direction, but assembled, in the axialdirection of the thermo roll, out of at least two shorter parts or theyare manufactured out of at least one part. The parts of the heattransfer layer 23′ or of the surface layer 24′ can be assembled togetherin the axial direction around a roll shaft 21′ that serves as theinnermost material layer and as the base of the thermo roll or around apreferably tubular roll shaft 21′ that is continuous/assembled ofseparate parts. To assure the stiffness of the thermo roll 20′ it may benecessary that only the heat transfer layer 23′ of the shell and, whenneeded, the surface layer 24′ are assembled in the manner describedabove, and the inner layer 21′ is a continuous, fairly stiff tubularpart 21′, for example, a forged steel shell. For the sake of clarity,FIG. 14A does not show the surface layer 24′ of the thermo roll 20′ asassembled around the heat transfer layer 23′.

The parts 231′, 232′, 233′, etc. shown in FIG. 14A, which parts can beassembled and which form the heat transfer layer 23′, can bemanufactured, for example, by forging, casting or by using thin rolledsheets available as ready-made sheets or by hot pressing. Themanufacture of the separate parts 231′, 232′, 233′, etc. forming theheat transfer layer 23′ in accordance with the second embodiment shownin FIG. 14A is not particularly described in this connection, butreference is made to the description of the hot pressing process inconnection with the first embodiment of the invention. The flow openingto be left in the parts can be machined or it is obtained as finished inthe casting or hot pressing process. The flow opening can be die cutinto thin parts.

In the second embodiment of the invention shown in FIG. 14A, the flowpassages 25′ or the flow openings 25′ are made beforehand in theseparate parts 231′, 232′, 233′, etc. before the assembly of the thermoroll 20′ such that, when the parts are fixed to one another, thepassages 25′ join and form a through-going system of passages 25′ in theassembled thermo roll. When the flow passages 25′ of the heat transfermedium can be placed in the shell structure already in the manufacturingstage, without needing to drill them into a full-size thermo roll,overlong drillings which are difficult during manufacture are avoided.

The separate parts 231′, 232′, 233′, etc. of FIG. 14A are providedalready before the assembly of the thermo roll 20′ with the possiblyneeded forms (not shown) required by the fixing and/or joint memberssuch that, when the shell parts are joined together, the fixing and/orjoint forms, for example, the holes of fixing bolts or joint forms withinterlocking shapes, fit one another. The mating surfaces of the parts231′, 232′, 233′, etc. are machined before assembly or they are alreadysufficiently smooth, for example, after hot pressing so that theassembled thermo roll 20′ will be tight. The different layers to beassembled on the continuous inner layer 21′ of FIG. 14A can be attachedto one another by welding, thermal contraction, soldering, or in asimilar manner, or by using bolts, for example, through the entirethermo roll 20′. In the latter case, the manufacture of the thermo roll20′ resembles the manufacture of the traditional filled roll, in whichthe shell of the roll is assembled by stacking and pressing sheets madeof fibers around a shaft. It is also possible to use an adhesive on thejoint surfaces to strengthen the joint. In addition, it may be necessaryto seal the joints to eliminate any leakages of the flow medium.

In the second embodiment of the invention, the material properties ofeach part assembled radially one within the other and/or axially oneafter the other, i.e. the material properties of the inner layer 21′,the parts 231′, 232′, 233′, etc. assembled one after the other andforming the heat transfer layer 23′, and the surface layer 24′, aredimensioned taking into account the final roll position of the part.

In the first embodiment of the invention, the material properties ofeach different material layer, i.e. the inner layer 11′, the heattransfer layer 13′ and the surface layer 14′, are dimensioned takinginto account the roll position of the layer.

At the web area in particular, the material layers of the layer on theinner side of the surface layer or the heat transfer layer 13′, 23′and/or the surface layer 14′, 24′ can be arranged to be of materialsthat are thermally more conductive than the materials outside the webarea. A material that is thermally less conductive is selected for thearea outside the web, so that the thermo roll is thermally lessconductive outside the web area than in the web area. In other words,the material layer of the thermo roll shell forming the heat transferlayer, is can be arranged to extend in the axial direction of the thermoroll substantially only across the width of the web area of the fibrousweb such that substantially outside the web area the shell of the thermoroll is formed of a material that is thermally less conductive than theheat transfer layer.

The flow passages 15′, 25′, 151′, 152′ and the flow tubes 16′ aredimensioned taking into account the position of the flow passage in theshell of the thermo roll. Thus, the flow in the flow passages 15′, 25′,151′, 152′ and in the flow tubes 16′ can be limited to assure theevenness of heat transfer, for example, by throttling the heat transferbores 15′, 152′, for example, over at least part of their length bymeans of tubes 16′, so that the cross-sectional area of the flow passage15′ is reduced and the flow velocity increases or the flow can beretarded by enlarging the size of the flow passages or tubes or thedirection of the flow in adjacent flow passages 15′ can be arranged indifferent directions.

Thus, in accordance with a variant of the first embodiment of theinvention, the flow diameter of the flow tubes 16′ forming the system offlow passages 15′ can increase or decrease depending on the location ofthe flow passage 15′ in the radial direction of the thermo roll anddepending on the location of the flow passage 15′ in the axial directionof the thermo roll such that the evenness of heat transfer is assured onthe outer surface 14 a′ of the thermo roll 10′.

To achieve a corresponding effect, the flow openings 25′ of the parts231′, 232′, 233′, etc., which form the heat transfer layer 23′ and areassembled one after the other as shown in FIG. 14A of the secondembodiment of the invention, can become smaller or larger in the axialdirection of the thermo roll 20′ such that the end result is flowpassages 25′ variable in diameter, which enables the evenness of heattransfer on the outer surface of the thermo roll 20′. In the separateparts 231′, 232′, 233′, etc. it is possible to construct a sufficientnumber of flow passages 25′, possibly in the radial direction atdifferent distances from the center line of the thermo roll 20′. Theheating and the cooling of the thermo roll can then be controlledaccording to the operating situation, for example, by guiding the flowthrough as many passages as possible in the heating and cooling stage,so that capacity is distributed into as large an area as possible.

In the normal operating situation, the flow can be guided only to someof the flow passages 15′, 25′, 151′, 152′, for example, to the passagessituated closest to the outer surface of the thermo roll. The flowpassage functions of the so-called end part (not shown in the figures),which are feed passages, leading to the flow passages of the shell, andtheir joining or branch connections, can be placed, for example, in anannular part assembled in the ends of the thermo roll. When desired, noactual end part is thus needed in the thermo roll 20′, but correspondingflow ducts are constructed in the outermost annular part of the shell ofthe thermo roll comprising a heat transfer layer situated mainly in theweb area. It is also possible to connect passages, when needed, closerto the middle of the thermo roll, farther away from the ends of thethermo roll, if it is considered necessary.

The connection and introduction of the flow passages 15′, 25′, 151′,152′ to the heat transfer layer 13′, 23′ can be selected in differentways. The passages can be passed even in the inner part of the thermoroll to the edge of the web area, from which they are passed in theradial direction through the inner layer 11′, 21′ of the shell up to theheat transfer layer 13′, 23′. Here the flow passages 15′, 25′, 151′,152′ can turn into the longitudinal direction of the thermo roll 10′,20′, 101′. A separate end part is not necessarily needed for heattransfer, so that the loss of heat in the end areas is reduced. The endpart needed for the thermo roll 10′, 20′, 101′ for some other reason canbe insulated with respect to the heat transfer layer situated in the webarea or the material of the end part can be selected such that the heattransfer in it in the axial direction and losses through the end surfaceare small. The material of said end part can also be fibrous,orthotropic or insulating.

The flow passages 15′, 25′, 151′, 152′ and the possible recesses orgrooves 12′ of the thermo roll are advantageously optimized in respectof their cross-sectional profile, size and cross-sectional area so as tobe exactly the kind of passages or parts of passages in which heattransfer between the medium and the outer surface of the thermo rollshell is as efficient and as even as possible. The location of the flowpassages 15′, 25′, 151′, 152′ in the radial direction, i.e. in the depthdirection, of the thermo roll is optimized taking into account theevenness requirements of heat. The cross-sectional profile of the flowpassages 15′, 25′, 151′, 152′ and the grooves 12′ of the thermo roll canalso be different from the conventional circular shape, for example,oval, angular or star-shaped.

In accordance with one embodiment of the invention, the heat transferlayer and the surface layer are made of a solid material into a part,for example, by hot pressing or by casting, before the assembly of thethermo roll or before the parts of the thermo roll are attached to oneanother. The layers of the finished thermo roll shell then comprisemainly two materials.

In accordance with one advantageous embodiment, the surface layer, whichis mainly of the same material, is layered in a different manufacturingstage by hot pressing, i.e. using hot isostatic pressing, on the innerlayer of the thermo roll shell, which is a forged tubular steel shell,the starting material of the surface layer to be hot pressed being inpowder form. By means of layers that are mainly of the same material itis possible to advantageously achieve a situation in which the differentlayers of the thermo roll shell have almost identical thermal expansion.In this way, the thermal stresses arising from variations in thetemperatures of the thermo roll shell are advantageously minimized. Ofcourse, the above-mentioned, for example, thin and hard coating canadditionally serve as a surface layer that is in contact with thefibrous web or the wire.

In accordance with one embodiment of the invention, the inner layer andthe surface layer are made of the same material, so that the layers ofthe shell of the finished thermo roll comprise mainly two materials.

In the method that employs the thermo roll of high heat transfer inaccordance with the invention, the fibrous web is brought into contactwith the surface 14 a′, 24 a′ of the thermo roll 10′, 20′, 101′. In themethod, when the thermo roll is heated, heat is transferred to thefibrous web across the heat transfer means of the thermo roll, such asthe heat transfer layer 13′, 23′ and/or the flow passages 15′, 25′,151′, 152′, and/or the outer surface 14 a′, 24 a′ of the thermo roll10′, 20′, 101′ serves as a support surface against which the fibrous webto be treated can be wet pressed, dried, calendered, glazed and/orcompacted and/or, when the thermo roll is cooled, heat is transferredout of the thermo roll and its shell across the heat transfer means.

The thermo roll 10′, 20′, 101′ of the invention intended for thetreatment of a fibrous web can be heated or cooled using heat transfermeans provided inside or outside the shell, advantageously internally,by means of a heat transfer medium. In addition, it is possible to useheating based on induction and/or friction and/or resistive heatingand/or heating based on condensation and/or hot air blowing.

In the first method in accordance with the invention for using thethermo roll 10′, 20′, 101′, which thermo roll is intended for thetreatment of a fibrous web and the shell of which thermo roll comprisesat least two material layers 11′, 13′, 14′, 21′, 23′, 24′, which thermoroll or the shell of which thermo roll is provided with heat transfermeans for heating and/or cooling the shell of the thermo roll,advantageously by means of a heat transfer medium, a heat capacity in arange of 100-300 kW/m, preferably in a range of 200-250 kW/m, istransferred to the fibrous web from the thermo roll 10′, 20′, 101′, theshell of which comprises at least two different material layers 11′,13′, 14′, 21′, 23′, 24′ which are arranged, using a manufacturingtechnique, radially one within the other, which material layers aremanufactured with respect to their manufacturing technique in differentstages or by different methods, a system of heat transfer medium flowpassages 15′, 25′, 151′, 152′ being placed in at least one of saidmaterial layers or confined by at least one of said material layersinside itself or situated in a boundary zone of said material layers,such that the temperature of the heat transfer medium is kept <350° C.

In the second method in accordance with the invention for using thethermo roll 10′, 20′, 101′, which thermo roll is intended for thetreatment of a fibrous web and the shell of which thermo roll comprisesat least two material layers 11′, 13′, 14′, 21′, 23′, 24′, which thermoroll or the shell of which thermo roll is provided with heat transfermeans for heating and/or cooling the shell of the thermo roll,advantageously by means of a heat transfer medium, a heat capacity in arange of 100-300 kW/m, preferably in a range of 200-250 kW/m, istransferred to the fibrous web from the thermo roll 10′, 20′, 101′, theshell of which comprises at least two material layers 11′, 13′, 14′,21′, 23′, 24′ which are placed radially one within the other and whichare different in their thermal conductivities, a system of heat transfermedium flow passages 15′, 25′, 30′, 151′, 152′ being placed in at leastone of said material layers or confined by at least one of said materiallayers inside itself or situated in a boundary zone of said materiallayers, such that the temperature of the heat transfer medium is kept<350° C.

In one application of the method in accordance with the invention forusing the thermo roll 10′, 20′, 101′, during the heating or cooling ofthe thermo roll, for example, when there is a transition from therunning state to the servicing state or vice versa, it is advantageousto use a separate heat transfer passage system 152′ in a material layer11′, 21′ that conducts less heat to even out the temperature differenceinside the thermo roll such that thermal stresses remain in a range thatcauses no fatigue in the structure.

It is recommended that the thermo roll used in the manufacture andfinishing of a fibrous web, in particular a low-gloss matte paper orboard, be used in the finishing line of the fibrous web in at least onenip in a device that calenders the fibrous web. Such devices, inparticular in the finishing of the fibrous web, include a multinipcalender, a soft calender, a machine calender, a belt calender, a metalbelt calender and a combination of these. The heatable and coolablethermo roll of the fibrous web machine is intended for the treatment ofthe fibrous web, for example, for pressing and/or calendering of thefibrous web in contact, i.e. a nip, between the thermo roll and abacking member in contact with the thermo roll.

It is recommended that in said at least one nip, in particular in a nipsituated in a finishing line, a thermo roll be used whose heat transfercapacity is high, of the order of 100-400 kW/m.

It is recommended that the flow passages of the thermo roll be placedcloser to the outer surface than normal, for example <55 mm to enhanceheat transfer.

It is recommended that those parts of the shell of the thermo roll whichare significant with respect to heat transfer be manufactured of amaterial that conducts heat well and whose thermal conductivity λ>70W/mK.

This material is selected in accordance with one embodiment of theinvention from a group that includes copper, ten, aluminum, zinc,chrome, zirconium or an equivalent metal material that conducts heatwell or an alloy or a composition metal formed of at least two of thesematerials. The metal material alloy is CuCrZr in accordance with oneembodiment.

It is recommended that the shell of the thermo roll be manufactured atleast partly by means of powder metallurgy.

Low-gloss matte paper or board is used as printing, art and photographicpaper/board. An essential feature is low gloss, matte quality, of thesurface, which nevertheless allows a high-quality and glossy printingresult. Thus, the surface of the thermo roll is advantageouslymanufactured to be porous and coarse in its microstructure such thatmatte quality is produced in calendering.

To manufacture high-quality matte paper, paper is calendered by means ofa porous and small-scale coarse thermo roll provided with a ceramiccoating. In accordance with an advantageous embodiment, a coating underthe trade name ValMatt is used as the ceramic coating of the thermoroll.

In the method for manufacturing a low-gloss fibrous web, such as mattepaper or board, in particular for finishing by calendering, which methoduses a thermo roll in accordance with the invention, a fibrous web iscalendered by the thermo roll in at least one nip in a multinip calenderor a soft calender or a machine calender or a belt calender or a metalbelt calender or in a combination of said calenders.

Advantageously, the fibrous web is calendered on the same calender assome other fibrous web grade such that said fibrous web is calenderedoperating with some of the nips using a smaller number of nips than whencalendering other fibrous web grades, in particular glossy grades.

Advantageously, the fibrous web is calendered in a separate nip which issituated in the finishing line and in which there is a thermo roll inaccordance with the invention, and which nip can be used or not usedwhen calendering other fibrous web grades, in particular glossy grades.

Advantageously, the calendering of the fibrous web is performed on anuncoated or coated fibrous web. The known methods of coating a fibrousweb include, among other things, blade coating, film transfer coatingand air brush coating as well as curtain coating and spray coating.

Above, the invention has been described only by way of example by meansof some of its advantageous embodiments. This is, of course, not meantto limit the present invention in any way to such single embodimentsbut, as is clear to a person skilled in the art, various alternativearrangements and modifications as well as applications are feasiblewithin the scope of protection defined by the appended claims.

1-111. (canceled)
 112. A thermo roll, in a fibrous web machine forpressing, drying, or cooling a fibrous web, comprising: a roll shellhaving an outer web engaging surface, and a thermal conductivity between300-350 W/mK.
 113. The thermo roll of claim 112 wherein the roll shellis a CuCrZr alloy (copper-chrome-zirconium), having a density of 8-10g/cm³ and an elastic modulus of 100-150 GPa.
 114. The thermo roll ofclaim 112 further comprising a wear resistant coating covering the outerweb engaging surface.
 115. A thermo roll, in a fibrous web machine forpressing, drying, or cooling a fibrous web, comprising: a rotatingcylindrical shell having an inner surface, and a central axis whichdefines an axial direction along the axis; a body formed of at least onepart, the body having an outer surface, the body arranged inside theshell; at least one heat transfer medium flow passage defined by theinner surface of the shell and the outer surface of the body; a quantityof heat transfer medium within the at least one heat transfer mediumflow passage; a first heat transfer medium conveying means for passingthe heat transfer medium into the at least one heat transfer medium flowpassage, the first heat transfer medium conveying means having aplurality of inlets into the at least one heat transfer medium flowpassage; a second heat transfer medium conveying means for removing theheat transfer medium from the at least one heat transfer medium flowpassage, the second heat transfer medium conveying means having aplurality of outlets from the at least one heat transfer medium flowpassage; a means for controlling flow of the heat transfer mediumbetween the first heat transfer medium conveying means and the secondheat transfer medium conveying means; wherein the inlets into the atleast one heat transfer medium flow passage are connected to the firstheat transfer medium conveying means, such that the heat transfer mediumis supplied into the at least one heat transfer medium flow passage atmore than one position along the axis of the cylindrical shell; andwherein the outlets from the at least one heat transfer medium flowpassage are connected to the second heat transfer medium conveyingmeans, such that the heat transfer medium is removed from the at leastone heat transfer medium flow passage at more than one position alongthe axis of the cylindrical shell.
 116. A method for manufacturing athermo roll for the treatment of a fibrous web, the method comprisingthe steps of: forming in a first stage a first layer of a shell of thethermo roll, of a first material with a first manufacturing technique;forming in a second stage a second layer of the shell of the thermo rollof a second material with a second manufacturing technique differentfrom the first manufacturing technique; arranging the first layerradially inwardly from the second layer of the shell of the thermo roll;forming heat transfer medium flow passages, each flow passage beingconfined within the first material layer, the second material layer, orsituated in a boundary zone between said first and second materiallayers; and heating the fibrous web with the shell of the thermo roll,with a heat transfer medium, and transferring 100-300 kW/m to thefibrous web with a heat transfer medium temperature of less than 350degrees C.
 117. The method of claim 116 wherein the step of transferring10-300 kW/m to the fibrous web is further limited to transferring200-250 kW/m to the fibrous web.